Problem 1 of 47
🐠

Fish Tank Problem

At a fish shop, Tank A had 544 more fish than Tank B. 86 fish were transferred from Tank A to Tank B such that Tank A had 4 times as many fish as Tank B. How many fish were there in Tank B at first?
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = Tank B after transfer
After the transfer, Tank A = 4 × Tank B.
Let Tank B (after) = 1 unit, so Tank A (after) = 4 units.

Use the bar model to see the transfer, then find the value of 3u:
Before transfer
Tank A
Tank B
86
86 fish sit in Tank A — press to transfer them to Tank B

After transfer
Tank A
Tank B
86
3u = =
2
Find the value of 1 unit
From Step 1: 3u = 372

1u = 372 ÷ 3 =
3
Find Tank B after the transfer
Tank B after the transfer = 1u = fish
4
Find original Tank B (before transfer)
Tank B received 86 fish, so it had 86 fewer before:

Tank B (before) = 1u − 86 = − 86 =

Tank B had fish at first.
💡 Hints:
Step 1: Difference = (4u+86)−(1u−86) = 3u+172 = 544. So 3u = 544−172 = 372.
Step 2: 1u = 372 ÷ 3 = 124.
Step 3: Tank B after = 1u = 124 fish.
Step 4: Tank B before = 124 − 86 = 38 fish.
💰

Jason & Don Problem

Jason had $120 more than Don. After he gave $24 to Don, Jason had 3 times as much money as Don. How much money did Jason have at first?
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = Don's amount after giving
After giving, Jason = 3 × Don.
Let Don (after) = 1 unit, so Jason (after) = 3 units.

Use the bar model to see the transfer, then find the difference:
Before giving
Jason
Don
$24
$24 sits with Jason — press to give it to Don

After giving
Jason
Don
$24
So:  2u = =
2
Find the value of 1 unit
From Step 1: 2u = 72

1u = 72 ÷ 2 =
3
Find Jason's amount after giving
Jason after = 3u = 3 × = $
4
Find Jason's original amount (before giving)
Jason gave away $24, so he had $24 more before:

Jason (before) = 3u + 24 = + 24 =

Jason had $ at first.
💡 Hints:
Step 1: Difference = (3u+24)−(1u−24) = 2u+48 = 120. So 2u = 120−48 = 72.
Step 2: 1u = 72 ÷ 2 = 36.
Step 3: Jason after = 3u = 3 × 36 = $108.
Step 4: Jason before = 108 + 24 = $132.
🌟

Jenny & Elly Stickers

Jenny had 12 more stickers than Elly at first. Jenny gave 48 of her stickers to Elly. In the end, Elly had 4 times as many stickers as Jenny. How many stickers did Jenny have at first?
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = Jenny's amount after giving
After giving, Elly = 4 × Jenny.
Let Jenny (after) = 1 unit, so Elly (after) = 4 units.

The total does not change — stickers are only moved, not added or removed.
Before giving: Jenny had 48 more → (1u + 48). Elly had 48 fewer → (4u − 48).

Use the bar model to see the transfer, then find the difference:
Before giving
Elly
Jenny
48
48 stickers sit with Jenny — press to give them to Elly

After giving
Elly
Jenny
So:  3u = + + =
2
Find the value of 1 unit
From Step 1: 3u = 84

1u = 84 ÷ 3 =
3
Find Jenny's amount after giving
Jenny after = 1u = stickers
4
Find Jenny's original amount (before giving)
Jenny gave away 48 stickers, so she had 48 more before:

Jenny (before) = 1u + 48 = + 48 =

Jenny had stickers at first.
💡 Hints:
Step 1: After giving 48: gap = 3u. Before giving: each side changes by 48, gap changes by 2×48=96. Jenny had 12 more → 3u = 96 − 12 = 84.
Step 2: 1u = 84 ÷ 3 = 28.
Step 3: Jenny after = 1u = 28 stickers.
Step 4: Jenny before = 28 + 48 = 76 stickers.
📁

Bookshop Files Problem

A school bookshop had twice as many blue files as red files in the morning. By end of the day, 45 blue files were sold and there were twice as many red files as blue files left. How many blue files were there at first?
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = blue files left at end
At end of day: Red = 2 × Blue left.
Let Blue (after) = 1 unit, so Red = 2 units.

Red files are not sold — the count stays the same all day.
So Red = 2u in the morning too.
Morning: Blue = 2 × Red = 2 × 2u = 4u.

Use the bar model to see the files sold, then find how many units were sold:
Morning (before)
Blue
1u
Red
2u
45 sold
45 blue files are in stock — press to sell them

End of day (after)
Blue
1u
Red
2u
Blue sold = 4u − 1u = 3u =
2
Find the value of 1 unit
3u = 45

1u = 45 ÷ 3 =
3
Find blue files at first
Blue files in morning = 4u = 4 × =

There were blue files at first.
💡 Hints:
Step 1: End of day: Red=2u, Blue(after)=1u. Red never changes, so morning Red=2u too. Morning Blue = 2×Red = 4u. Sold = 4u−1u = 3u = 45.
Step 2: 3u = 45, so 1u = 45 ÷ 3 = 15.
Step 3: Blue in morning = 4u = 4 × 15 = 60.
🍪

Ivy's Cookies & Muffins

Ivy made 4 times as many cookies as muffins for a party. After 84 cookies were eaten, there were twice as many muffins as cookies left. How many cookies and muffins did Ivy make in all?
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = cookies left after eating
After eating: Muffins = 2 × Cookies left.
Let Cookies (after) = 1 unit, so Muffins = 2 units.

Muffins are not eaten — the count stays the same throughout.
So Muffins = 2u always. Before eating: Cookies = 4 × Muffins = 4 × 2u = 8u.

Use the bar model to see the cookies eaten, then solve:
Before (party starts)
Cookies
Muffins
2u
84 eaten
84 cookies will be eaten — press to see what's left

After (cookies eaten)
Cookies
Muffins
2u
Eaten = Cookies(before) − Cookies(after) = 8u − 1u = 7u
So:  7u =
2
Find the value of 1 unit
7u = 84

1u = 84 ÷ 7 =
3
Find total cookies and muffins made
Cookies made = 8u = 8 × =

Muffins made = 2u = 2 × =

Total = + =

Ivy made cookies and muffins in all.
💡 Hints:
Step 1: Let Cookies(after)=1u, Muffins=2u. Before: Cookies=4×2u=8u. Eaten = 8u−1u = 7u = 84.
Step 2: 1u = 84 ÷ 7 = 12.
Step 3: Cookies = 8×12 = 96. Muffins = 2×12 = 24. Total = 96+24 = 120.
🛍️

Kim & Tina Shopping

Kim and Tina went shopping with the same amount of money. Kim spent $180 and Tina spent $70. Tina had 3 times as much money left as Kim. How much money did each girl have at first?
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = Kim's money left
After shopping: Tina = 3 × Kim left.
Let Kim (after) = 1 unit, so Tina (after) = 3 units.

Since they started with the same amount:
Kim (before) = 1u + 180    Tina (before) = 3u + 70

Use the bar model to see the spending, then find the difference:
Before shopping (equal start)
Kim
1u
$180
Tina
3u
$70
Both start equal — press to see what each spends

After shopping
Kim
1u
Tina
3u
Since they started equal: 1u + 180 = 3u + 70
So: 2u = =
2
Find the value of 1 unit
2u = 110

1u = 110 ÷ 2 =
3
Find how much each girl had at first
Each girl's amount = 1u + 180 = 3u + 70

= + 180 = $

Each girl had $ at first.
💡 Hints:
Step 1: Equal start: 1u+180 = 3u+70 → 180−70 = 3u−1u → 2u = 110.
Step 2: 1u = 110 ÷ 2 = 55.
Step 3: Each had 1u + 180 = 55 + 180 = $235.
👚

Fiona's Shirts & Blouses

Fiona bought 3 shirts and 4 blouses for $176. Each shirt cost ½ as much as a blouse. How much did each shirt cost?
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = cost of 1 shirt
Each shirt costs ½ as much as a blouse.
Let 1 shirt = 1 unit, so 1 blouse = 2 units.

Use the bar model to count all the units:
Shirts
1u
1u
1u
Blouses
2u
2u
2u
2u
3 shirts + 4 blouses = 3u + 8u = 11u = $176
Total units = 3u + 4 × 2u = 3u + 8u = u
2
Find the value of 1 unit
11u = $176

1u = $176 ÷ 11 = $
3
Find the cost of each shirt
1 shirt = 1u = $

Each shirt cost $.
💡 Hints:
Step 1: Shirt = 1u, Blouse = 2u. Total = 3×1u + 4×2u = 3u + 8u = 11u.
Step 2: 11u = $176, so 1u = 176 ÷ 11 = $16.
Step 3: Each shirt = 1u = $16.
👟

Ivy's Shorts & Shoes

Ivy bought 3 pairs of shorts and 4 pairs of shoes for $181. Each pair of shoes cost $12 more than a pair of shorts. How much did each pair of shoes cost?
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = cost of 1 pair of shorts
Let 1 pair of shorts = 1 unit.
Then 1 pair of shoes = 1 unit + $12.

Use the bar model to count all the units and extras:
Shorts
1u
1u
1u
Shoes
1u
+$12
1u
+$12
1u
+$12
1u
+$12
3u + 4u + (4 × $12) = 7u + $48 = $181
Total = 7u + 48 = 181
7u = 181 − 48 =
2
Find the value of 1 unit
7u = 133

1u = 133 ÷ 7 = $
3
Find the cost of each pair of shoes
1 pair of shoes = 1u + $12 = $ + $12 = $

Each pair of shoes cost $.
💡 Hints:
Step 1: Shorts=1u, Shoes=1u+$12. Total = 3u + 4(1u+12) = 7u+48 = 181 → 7u = 133.
Step 2: 1u = 133 ÷ 7 = $19.
Step 3: Shoes = 19 + 12 = $31.
🔑

Angela's Keychains

Angela made a total of 55 keychains in 5 days. Each day, she made 3 more keychains than the day before. How many keychains did Angela make on the last day?
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = keychains made on Day 1
Let Day 1 = 1 unit. Each day adds 3 more:
Day 1 = 1u   Day 2 = 1u+3   Day 3 = 1u+6   Day 4 = 1u+9   Day 5 = 1u+12

Use the bar model to see the pattern, then find the totals:
Day 1
1u
Day 2
1u
+3
Day 3
1u
+6
Day 4
1u
+9
Day 5
1u
+12
5u + (0+3+6+9+12) = 5u + 30 = 55
Total extras = 0+3+6+9+12 =
5u = 55 − =
2
Find the value of 1 unit
5u = 25

1u = 25 ÷ 5 =
3
Find keychains on Day 5 (last day)
Day 5 = 1u + 12 = + 12 =

Angela made keychains on the last day.
💡 Hints:
Step 1: Extras = 0+3+6+9+12 = 30. So 5u = 55−30 = 25.
Step 2: 1u = 25 ÷ 5 = 5.
Step 3: Day 5 = 1u+12 = 5+12 = 17.
👢

Boots, Shoes & Sandals

The total cost of a pair of boots, a pair of shoes and a pair of sandals is $211. A pair of boots costs $43 more than a pair of shoes. A pair of shoes costs 3 times as much as a pair of sandals. Find the cost of a pair of boots.
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = cost of a pair of sandals
Let sandals = 1u.
Shoes = 3 × sandals = 3u.
Boots = shoes + $43 = 3u + $43.

Use the bar model to see all three items, then find the total units:
Sandals
1u
Shoes
3u
Boots
3u
+$43
1u + 3u + (3u + $43) = 7u + $43 = $211
7u = $211 − $43 = $
2
Find the value of 1 unit
7u = $168

1u = $168 ÷ 7 = $
3
Find the cost of a pair of boots
Boots = 3u + $43
= 3 × $ + $43
= $ + $43
= $

A pair of boots costs $.
💡 Hints:
Step 1: Sandals=1u, Shoes=3u, Boots=3u+$43. Total = 7u+43=211 → 7u=168.
Step 2: 1u = 168 ÷ 7 = $24.
Step 3: Boots = 3×24+43 = 72+43 = $115.
👜

Key Pouch, Wallet & Bag

Ivan bought a key pouch, a wallet and a bag for $258. The wallet cost $12 more than the key pouch. The bag cost 3 times as much as the wallet. Find the cost of the key pouch.
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = cost of the key pouch
Let key pouch = 1u.
Wallet = 1u + $12.
Bag = 3 × wallet = 3 × (1u + $12) = 3u + $36.

Use the bar model to see all three items:
Pouch
1u
Wallet
1u
+$12
Bag
3u
+$36
1u + (1u+$12) + (3u+$36) = 5u + $48 = $258
5u = $258 − $48 = $
2
Find the value of 1 unit
5u = $210

1u = $210 ÷ 5 = $
3
Find the cost of the key pouch
Key pouch = 1u = $

The key pouch costs $.
💡 Hints:
Step 1: Pouch=1u, Wallet=1u+$12, Bag=3×(1u+$12)=3u+$36. Total=5u+$48=$258 → 5u=$210.
Step 2: 1u = $210 ÷ 5 = $42.
Step 3: Key pouch = 1u = $42.
🍚

Rice Cooker, Hair Dryer & Oven

Angela bought a rice cooker, a hair dryer and an oven for $272. The rice cooker cost 3 times as much as the hair dryer. The oven cost $15 less than the rice cooker. Find the cost of the rice cooker.
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = cost of the hair dryer
Let hair dryer = 1u.
Rice cooker = 3 × hair dryer = 3u.
Oven = rice cooker − $15 = 3u − $15.

Use the bar model to see all three items:
Dryer
1u
Cooker
3u
Oven
3u−$15
−$15
1u + 3u + (3u − $15) = 7u − $15 = $272
7u = $272 + $15 = $
2
Find the value of 1 unit
7u = $287

1u = $287 ÷ 7 = $
3
Find the cost of the rice cooker
Rice cooker = 3u = 3 × $ = $

The rice cooker costs $.
💡 Hints:
Step 1: Dryer=1u, Cooker=3u, Oven=3u−$15. Total=7u−$15=$272 → 7u=$287.
Step 2: 1u = $287 ÷ 7 = $41.
Step 3: Rice cooker = 3×$41 = $123.
📦

Box & Books

The mass of a box and 8 identical books is 3410 g. The mass of the same box with 5 identical books is 2300 g. Find the mass of the box.
📋 Working Steps — Fill in the blanks!
1
Find the mass of 1 book
Both situations have the same box. Subtracting removes the box:
(Box + 8 books) − (Box + 5 books) = 3 books

Use the bar model to see the difference:
8 books
Box
8 books
= 3410 g
5 books
Box
5 books
= 2300 g
3 books = 3410 − 2300 = 1110 g  →  1 book = 1110 ÷ 3 = 370 g
3 books = 3410 − 2300 = g
1 book = ÷ 3 = g
2
Find the mass of the box
Using Box + 5 books = 2300 g:

5 books = 5 × = g

Box = 2300 − = g

The mass of the box is g.
💡 Hints:
Step 1: Same box in both. Subtract: (8−5) = 3 books = 3410−2300 = 1110 g → 1 book = 370 g.
Step 2: 5 books = 5×370 = 1850 g. Box = 2300−1850 = 460 g.
🍊

Box, Oranges & Apples

The total mass of a box and some oranges was 25 kg. The total mass of the same box and some apples was 11 kg. The mass of the oranges was 3 times the mass of the apples. What is the mass of the box?
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = mass of apples
Let apples = 1u, so oranges = 3u.

Box + 3u = 25 kg
Box + 1u = 11 kg

Subtracting removes the box — use the bar model to see the difference:
Oranges
Box
3u
= 25 kg
Apples
Box
1u
= 11 kg
3u − 1u = 2u = 25 − 11 = 14 kg  →  1u = 7 kg
2u = 25 − 11 = kg
1u = ÷ 2 = kg
2
Find the mass of the box
Using Box + 1u = 11 kg:

Box = 11 − = kg

The mass of the box is kg.
💡 Hints:
Step 1: Apples=1u, Oranges=3u. Subtract rows: 2u = 25−11 = 14 kg → 1u = 7 kg.
Step 2: Box = 11 − 1u = 11 − 7 = 4 kg.
🍎

Box, Apples & Oranges

The mass of a box and some apples is 560 g. The mass of the same box with some oranges is 1240 g. Given the mass of all the oranges is 3 times the mass of all the apples, find the mass of the box.
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = mass of apples
Let apples = 1u, so oranges = 3u.

Box + 1u = 560 g
Box + 3u = 1240 g

Subtracting removes the box — use the bar model to see the difference:
Apples
Box
1u
= 560 g
Oranges
Box
3u
= 1240 g
3u − 1u = 2u = 1240 − 560 = 680 g  →  1u = 340 g
2u = 1240 − 560 = g
1u = ÷ 2 = g
2
Find the mass of the box
Using Box + 1u = 560 g:

Box = 560 − = g

The mass of the box is g.
💡 Hints:
Step 1: Apples=1u, Oranges=3u. Subtract rows: 2u = 1240−560 = 680 g → 1u = 340 g.
Step 2: Box = 560 − 1u = 560 − 340 = 220 g.
🎡

Carnival Tickets

At a carnival, the entrance ticket for an adult was $2 and $1 for a child. There was an equal number of adults and children. The total amount collected was $228. How many people were at the carnival?
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = number of adults = number of children
Since there are equal numbers, let adults = children = 1u (people).

Total collected from adults = 1u × $2 = $2u
Total collected from children = 1u × $1 = $1u

Use the bar model to see the total collected:
Adults
1u × $2 = $2u
Children
1u × $1 = $1u
$2u + $1u = $3u = $228
3u = $228
1u = $228 ÷ 3 =

So there were adults and children.
2
Find the total number of people
Total people = adults + children

= + =

There were people at the carnival.
💡 Hints:
Step 1: Adults=1u people × $2 = $2u. Children=1u people × $1 = $1u. Total = $3u = $228 → 1u = 76.
Step 2: Total people = 76 + 76 = 152.
🥮

Egg Tarts & Cheese Tarts

Peggy bought an equal number of egg tarts and cheese tarts for $60.
1 egg tart cost $2 and 1 cheese tart cost $3.
How many egg tarts did Peggy buy?
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = number of egg tarts = number of cheese tarts
Since equal numbers, let egg tarts = cheese tarts = 1u.

Total from egg tarts  = 1u × $2 = $2u
Total from cheese tarts = 1u × $3 = $3u

Use the bar model to see the total spent:
Egg
1u × $2 = $2u
Cheese
1u × $3 = $3u
$2u + $3u = $5u = $60
5u = $60
1u = $60 ÷ 5 =
2
Find the number of egg tarts
Number of egg tarts = 1u =

Peggy bought egg tarts.
💡 Hints:
Step 1: Equal numbers → egg=1u, cheese=1u. Total = 1u×$2 + 1u×$3 = $5u = $60 → 1u = 12.
Step 2: Egg tarts = 1u = 12.
📓

Notebooks & Files

Helen bought an equal number of notebooks and files. 1 notebook cost twice as much as a file. 1 file cost $6. She spent a total of $90. How many files did she buy?
📋 Working Steps — Fill in the blanks!
1
Find the cost of 1 notebook
1 file = $6
1 notebook = 2 × $6 = $
2
Let 1 unit = number of notebooks = number of files
Since equal numbers, let notebooks = files = 1u.

Total from notebooks = 1u × $12 = $12u
Total from files     = 1u × $6 = $6u

Use the bar model to see the total spent:
Books
1u × $12 = $12u
Files
1u × $6 = $6u
$12u + $6u = $18u = $90
18u = $90
1u = $90 ÷ 18 =
3
Find the number of files
Number of files = 1u =

Helen bought files.
💡 Hints:
Step 1: Notebook = 2 × $6 = $12.
Step 2: Equal numbers → 1u each. Total = $12u + $6u = $18u = $90 → 1u = 5.
Step 3: Files = 1u = 5.
🍽️

Buffet Dinner Discount

A group of 20 people ate at the buffet dinner. The price was $20 per person with a $6 discount for every 5 people. How much did they have to pay?
📋 Working Steps — Fill in the blanks!
1
Break 20 people into groups of 5
20 ÷ 5 = groups of 5
20 people = 4 groups of 5
5 people
× $20
−$6
5 people
× $20
−$6
5 people
× $20
−$6
5 people
× $20
−$6
Total cost = 4 × $100 = $
Total discount = 4 × $6 = $
2
Find the amount to pay
Amount to pay = $400 − $ = $

They had to pay $.
💡 Hints:
Step 1: 20 × $20 = $400.
Step 2: 20 ÷ 5 = 4 groups → 4 × $6 = $24 discount.
Step 3: $400 − $24 = $376.
🍽️

Buffet Dinner (32 people)

A group of 32 people ate at a buffet dinner. The price was $20 per person with a $6 discount for every 5 people. How much did they have to pay?
📋 Working Steps — Fill in the blanks!
1
Break 32 people into groups of 5
32 ÷ 5 = groups remainder
32 people = 6 groups of 5 + 2 leftover
5 ppl
×$20
−$6
5 ppl
×$20
−$6
5 ppl
×$20
−$6
5 ppl
×$20
−$6
5 ppl
×$20
−$6
5 ppl
×$20
−$6
2 ppl
×$20
Total cost = 32 × $20 = $
Total discount = 6 × $6 = $
2
Find the amount to pay
Amount to pay = $640 − $ = $

They had to pay $.
💡 Hints:
Step 1: 32 ÷ 5 = 6 remainder 2. Only 6 full groups get the discount. Total = 32×$20 = $640. Discount = 6×$6 = $36.
Step 2: $640 − $36 = $604.
🍽️

How Many People? (Reverse)

Mr Samad paid $812 for a buffet dinner. The price was $20 per person with a $6 discount for every 5 people. How many people did he pay for?
📋 Working Steps — Fill in the blanks!
1
Find the net cost per group of 5
Each group of 5 people pays $100 but gets $6 off:
1 group of 5 = $100 − $6 = $

The bar model shows 1 group — how many such groups fit into $812?
1 group of 5 people
5 ppl
×$20
−$6
= $94
× ? groups
Number of full groups = $812 ÷ $94 = remainder $
2
Find the leftover people and total
Leftover amount $60 ÷ $20 = more people

Total people = 8 × 5 + =

Mr Samad paid for people.
💡 Hints:
Step 1: 1 group of 5 = $100 − $6 = $94. Groups = $812 ÷ $94 = 8 remainder $60.
Step 2: Leftover $60 ÷ $20 = 3 more people. Total = 8×5 + 3 = 43 people.
🌾

Rice Packets

A grocer has a sack of rice with a mass of 62 kg. The rice was repacked into packets of 3 kg each.
(a) How many packets of rice can be packed?
(b) What was the mass of the remaining rice?
📋 Working Steps — Fill in the blanks!
1
Divide 62 kg into 3 kg packets
62 ÷ 3 = remainder kg
62 kg = 20 packets of 3 kg + 2 kg remaining
3 kg packet (×20)
2 kg remaining
2a
How many packets can be packed?
Number of 3 kg packets =

packets of rice can be packed.
2b
What is the mass of the remaining rice?
Mass of remaining rice = kg

The remaining rice has a mass of kg.
💡 Hints:
Step 1: 62 ÷ 3 = 20 remainder 2.
(a): 20 packets can be packed.
(b): 2 kg of rice remains.
🚌

Buses for Sports Day

A group of Primary 5 pupils were going to the stadium by bus for Sports Day. There were 257 pupils. Each bus could carry 42 pupils. How many buses were needed?
📋 Working Steps — Fill in the blanks!
1
Divide 257 pupils into groups of 42
257 ÷ 42 = remainder pupils
257 pupils = 6 full buses + 5 remaining
42
42
42
42
42
42
5
⚠️ The 5 remaining pupils still need a bus — even though it is not full!
Full bus (42 pupils)
5 pupils — needs 1 more bus
2
Find the number of buses needed
6 full buses + 1 bus for the remaining 5 pupils

Total buses needed = 6 + 1 =

buses were needed.
💡 Hints:
Step 1: 257 ÷ 42 = 6 remainder 5.
Step 2: 6 full buses + 1 extra bus for the 5 remaining pupils = 7 buses.
• Remember: even if the last bus isn't full, you still need it!
🔌

Wire Pieces

A coil of wire 980 m long is cut into equal pieces of 30 m each. What is the greatest number of such pieces that can be cut?
📋 Working Steps — Fill in the blanks!
1
Divide 980 m into 30 m pieces
980 ÷ 30 = remainder m
980 m = 32 pieces of 30 m + 20 m leftover
30
20
⚠️ The 20 m leftover is not enough for another 30 m piece — it is discarded.
30 m piece (×32)
20 m leftover (discarded)
2
State the greatest number of pieces
The 20 m remainder cannot make another 30 m piece, so it is not counted.

Greatest number of 30 m pieces =

The greatest number of pieces that can be cut is .
💡 Hints:
Step 1: 980 ÷ 30 = 32 remainder 20.
Step 2: The 20 m leftover cannot make a full 30 m piece, so the answer is 32 pieces.
• Unlike the buses problem, here the remainder is simply discarded — do NOT add 1!
✏️

Files & Pens

2 files and 3 pens cost $20.
4 files and 7 pens cost $42.
What is the cost of 1 pen?
📋 Working Steps — Fill in the blanks!
1
Make the number of files equal
Equation 1: 2f + 3p = $20
Equation 2: 4f + 7p = $42

Multiply Equation 1 by :
4f + p = $  …(3)
Bar model — aligning the files
Eqn 1
f
f
p
p
p
= $20
Eqn 2
f
f
f
f
p
p
p
p
p
p
p
= $42
Eqn 3
f
f
f
f
p
p
p
p
p
p
= $40
File (f)
Pen (p)
2
Subtract to find the cost of 1 pen
Eqn 2 − Eqn 3: (4f + 7p) − (4f + 6p) = $42 − $40

1p = $

1 pen costs $.
💡 Hints:
Step 1: Multiply Eqn 1 by 2: 4f+6p=$40 (Eqn 3).
Step 2: Eqn 2 − Eqn 3: 1p = $42−$40 = $2.
👔

Shirts, Pants & Ties

2 shirts and 4 pairs of pants cost $144.
3 shirts and 6 ties cost $126.
The cost of 1 pair of pants equals the cost of 3 ties.
Find the cost of 1 shirt.
📋 Working Steps — Fill in the blanks!
1
Replace pants with ties using the given relationship
1 pair of pants = 3 ties, so 4 pairs of pants = ties

Rewrite Equation 1: 2s + t = $144  …(3)
2
Make the number of ties equal
Equation 2: 3s + 6t = $126
Multiply Equation 2 by :
s + 12t = $  …(4)
Bar model after substitution — aligning the ties
Eqn 3
s
s
12t
= $144
Eqn 4
s
s
s
s
s
s
12t
= $252
Shirt (s)
12 ties (12t)
3
Subtract to find the cost of 1 shirt
Eqn 4 − Eqn 3: (6s + 12t) − (2s + 12t) = $252 − $144

4s = $
1s = $

1 shirt costs $.
💡 Hints:
Step 1: 4p = 4×3t = 12t. Rewrite Eqn 1: 2s+12t=$144 (Eqn 3).
Step 2: Eqn 2 × 2: 6s+12t=$252 (Eqn 4).
Step 3: Eqn 4−Eqn 3: 4s=$108 → s=$27.
🍽️

Plates & Bowls

Mrs Tan paid $143.40 for some plates and bowls. A plate costs $6.40 and a bowl costs $1.70 less. Mrs Tan bought 12 more plates than bowls. How many plates did she buy?
📋 Working Steps — Fill in the blanks!
1
Find the cost of 1 bowl
1 bowl = $6.40 − $1.70 = $
2
Let 1 unit = number of bowls
Let bowls = 1u. Then plates = 1u + 12.

Cost of 12 extra plates = 12 × $6.40 = $

Remaining cost (for u bowls + u plates) = $143.40 − $ = $
After removing the 12 extra plates cost ($76.80)
Per unit
u×$4.70
u×$6.40
= $66.60
u bowls × $4.70
u plates × $6.40
Cost per unit pair = $4.70 + $6.40 = $
Number of units = $66.60 ÷ $ =
3
Find the number of plates
Bowls = 1u =
Plates = 1u + 12 = + 12 =

Mrs Tan bought plates.
💡 Hints:
Step 1: Bowl = $6.40−$1.70 = $4.70.
Step 2: 12 extra plates = 12×$6.40 = $76.80. Remaining = $143.40−$76.80 = $66.60. Per unit = $4.70+$6.40 = $11.10. Units = $66.60÷$11.10 = 6.
Step 3: Plates = 6+12 = 18.
🎂

Age Problem

Mr Ng is 47 years old now. His son is 8 years old. In how many years' time will Mr Ng be 4 times as old as his son?
📋 Working Steps — Fill in the blanks!
1
Find the age gap (stays constant)
Age gap = 47 − 8 = years

This gap never changes — both age by the same amount each year.
2
Let 1 unit = son's age in the future
In x years: Mr Ng = 4 × Son → Son = 1u, Mr Ng = 4u.

Age gap = 4u − 1u = 3u =
In x years' time
Son
1u
Mr Ng
1u
4u
3u = 39  →  1u = 13 (son's future age)
1u = 39 ÷ 3 =
3
Find how many years from now
Son's future age = 1u = years old

Years from now = − 8 =

In years' time, Mr Ng will be 4 times as old as his son.
💡 Hints:
Step 1: Age gap = 47−8 = 39. This stays constant forever.
Step 2: Future: Son=1u, Mr Ng=4u. Gap=3u=39 → 1u=13.
Step 3: Son's future age=13. Years = 13−8 = 5.
👨‍👦

Combined Age

Mr Lim is 40 years old now. His son is 24 years younger than him. What will be their combined age three years later?
📋 Working Steps — Fill in the blanks!
1
Find the son's current age
Son's age now = 40 − 24 = years old
2
Find their ages in 3 years
In 3 years, both age by 3:
Mr Lim
40
+3
Son
16
+3
Combined now = 40 + 16 = 56  |  Each ages +3 → combined +6
Mr Lim in 3 years = 40 + 3 =
Son in 3 years = 16 + 3 =
3
Find their combined age
Combined age = + =

Their combined age three years later will be .
💡 Hints:
Step 1: Son now = 40−24 = 16.
Step 2: Mr Lim in 3 years = 43. Son in 3 years = 19.
Step 3: Combined = 43+19 = 62. (Or: 40+16+3+3 = 56+6 = 62.)
🎂

Simon & Alice Ages

Simon is 3 times as old as Alice. In 7 years' time, their total age will be 78 years. What is Alice's age now?
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = Alice's age now
Let Alice = 1u, so Simon = 3u.

In 7 years: Alice = 1u + 7, Simon = 3u + 7.
Total = (1u + 7) + (3u + 7) = 4u + 14 = 78

Use the bar model to see the future ages, then solve:
Alice
1u
+7
Simon
1u
3u
+7
4u + 14 = 78  →  4u = 78 − 14 = 64  →  1u = 16
Remove the two +7 strips: 4u = 78 − =
1u = ÷ 4 =
2
Find Alice's age now
Alice's age now = 1u = years old

Alice is years old now.
💡 Hints:
Step 1: Alice=1u, Simon=3u. In 7 years: (1u+7)+(3u+7)=4u+14=78. Remove 14: 4u=64 → 1u=16.
Step 2: Alice now = 1u = 16.
🐟

Fractions of Fish

At a fish shop, there are guppies, goldfish and angelfish. 15 of the fish are guppies, 14 of the fish are goldfish and the rest are angelfish. What fraction of the fish are angelfish?
📋 Working Steps — Fill in the blanks!
1
Find the total number of units using LCM
Denominators are 5 and 4. LCM =

Let total = 20 units.
Guppies  = 15 × 20 = units
Goldfish = 14 × 20 = units
2
Find the angelfish units
Angelfish = 20 − = units
20 units total
4u
5u
11u
Guppies (4u = 15)
Goldfish (5u = 14)
Angelfish (11u)
3
Write the fraction of angelfish
Fraction of angelfish =

of the fish are angelfish.
💡 Hints:
Step 1: LCM(5,4)=20. Guppies=15×20=4u. Goldfish=14×20=5u.
Step 2: Angelfish=20−4−5=11u.
Step 3: Fraction = 1120.
🧵

Red, Blue & Green Buttons

A seamstress has 400 red, blue and green buttons. 310 of the buttons are red. 14 of the buttons are blue and the rest are green. How many green buttons does the seamstress have?
📋 Working Steps — Fill in the blanks!
1
Find the total number of units using LCM
Denominators are 10 and 4. LCM =

Let total = 20 units.   1u = 400 ÷ 20 =

Red  = 310 × 20 = units
Blue = 14 × 20 = units
2
Find the number of green buttons
Green = 20 − = units
20 units = 400 buttons
6u
5u
9u
Red (6u = 310)
Blue (5u = 14)
Green (9u = ?)
Green buttons = 9u = 9 × = buttons

The seamstress has green buttons.
💡 Hints:
Step 1: LCM(10,4)=20. 1u=400÷20=20. Red=6u, Blue=5u.
Step 2: Green=20−6−5=9u. 9u=9×20=180 buttons.
🔮

Harry's Marbles

Harry had 208 marbles. He gave 18 of the marbles to his friends and 14 of the marbles to his neighbour. How many marbles did he have left?
📋 Working Steps — Fill in the blanks!
1
Find the total number of units using LCM
Denominators are 8 and 4. LCM =

Let total = 8 units.   1u = 208 ÷ 8 =

Friends   = 18 × 8 = unit(s)
Neighbour = 14 × 8 = unit(s)
2
Find the units left
Left = 8 − = units
8 units = 208 marbles
1u
2u
5u
Friends (1u = 18)
Neighbour (2u = 14)
Left (5u)
3
Find the number of marbles left
Marbles left = 5u = 5 × =

Harry had marbles left.
💡 Hints:
Step 1: LCM(8,4)=8. 1u=208÷8=26. Friends=18×8=1u. Neighbour=14×8=2u.
Step 2: Left=8−1−2=5u.
Step 3: 5u=5×26=130 marbles.
🍪

Grace's Cookies

Grace baked some cookies. She gave 35 cookies to her neighbours and 14 of the remainder to her friends. In the end, she had 24 cookies left. How many cookies did Grace bake?
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = cookies given to friends
After giving to neighbours, the remainder is split:
14 of remainder → friends  = 1u
34 of remainder → kept     = 3u = 24

Use the bar model to see the remainder split:
35
1u
4u=32
Friends (¼ of remainder)
Kept (24 cookies)
Neighbours (35)
3u = 24 → 1u = 24 ÷ 3 =
2
Find the remainder and total
Remainder = 4u = 4 × = cookies

Total cookies baked = 35 + =

Grace baked cookies.
💡 Hints:
Step 1: 34 of remainder = 24 = 3u → 1u = 8. Remainder = 4u = 32.
Step 2: Total = 35 + 32 = 67 cookies.
🍪

Gracia's Cookies

Gracia baked some cookies. She gave 35 cookies to her neighbours and 14 of the remainder to her friends. In the end, she had 13 of the cookies she baked left. How many cookies did Gracia bake?
📋 Working Steps — Fill in the blanks!
1
Let 1 unit = cookies given to friends
After giving to neighbours, the remainder is split:
14 of remainder → friends = 1u
34 of remainder → kept    = 3u

Kept = 13 of total baked → total = 3 × kept = 3 × 3u = 9u
5u=35
1u
3u
Neighbours (5u=35)
Friends (1u)
Kept (3u = 13 of total)
2
Find the value of 1 unit
Neighbours = total − remainder = 9u − 4u = u = 35
1u = 35 ÷ =
3
Find total cookies baked
Total = 9u = 9 × =

Gracia baked cookies.
💡 Hints:
Step 1: Remainder=4u (friends=1u, kept=3u). Kept=13 of total → total=9u.
Step 2: Neighbours=9u−4u=5u=35 → 1u=7.
Step 3: Total=9×7=63 cookies.
🎡

Funfair Boys & Girls

There was a total of 400 boys and girls at a funfair. 45 of the children are boys and the rest are girls. 34 of the boys and 15 of the girls left the funfair. How many more boys than girls remained?
📋 Working Steps — Fill in the blanks!
1
Find the number of boys and girls
Boys = 45 × 400 =
Girls = 15 × 400 =
2
Find how many boys and girls remained
Boys who left = 34 × 320 =
Boys remained = 320 − =

Girls who left = 15 × 80 =
Girls remained = 80 − =
After some left the funfair
Boys
left 240
rem 80
= 320
Girls
left 16
rem 64
= 80
3
Find how many more boys than girls remained
More boys than girls = =

There were more boys than girls remaining.
💡 Hints:
Step 1: Boys=45×400=320. Girls=15×400=80.
Step 2: Boys left=34×320=240 → remained=80. Girls left=15×80=16 → remained=64.
Step 3: 80−64=16 more boys.
🧵

Fiona's Cloth

Fiona had 5 m of cloth. She used 12 of it to make a dress and 12 m to sew a small bag. How much cloth did she have left?
📋 Working Steps — Fill in the blanks!
1
Find cloth used for the dress
Cloth for dress = 12 × 5 m = m
5 m of cloth
dress 2.5 m
bag
0.5 m
left
Dress (12 of 5 m = 2.5 m)
Bag (0.5 m)
Left (?)
2
Find cloth left
Total used = dress + bag = + = m

Cloth left = 5 − = m

Fiona had m of cloth left.
💡 Hints:
Step 1: Dress = 12 × 5 = 2.5 m.
Step 2: Total used = 2.5 + 0.5 = 3 m. Left = 5 − 3 = 2 m.
🧁

Mrs Lim's Sugar

Mrs Lim has 34 kg of sugar. She used 18 kg to make some cupcakes and 310 of the remaining sugar to bake some muffins. How many kilograms of sugar did she use to make the muffins? Express your answer in simplest form.
📋 Working Steps — Fill in the blanks!
1
Find the remaining sugar after cupcakes
Remaining = 3418 = kg
34 kg of sugar
18 kg
remaining 58 kg
Remaining 58 kg split
310 muffins
710 left
Cupcakes (18 kg)
Muffins (310 of remaining)
2
Find the sugar used for muffins
Muffins = 310 × remaining = 310 × = kg

Mrs Lim used kg of sugar for muffins.
💡 Hints:
Step 1: Remaining = 3418 = 6818 = 58 kg.
Step 2: Muffins = 310 × 58 = 1580 = 316 kg.
🍊

Siti's Orange Juice

Siti prepared 112 of orange juice. She poured 110 ℓ for her brother. She then poured 34 of the remaining juice into a flask. She drank the rest. How much juice did Siti drink? Express your answer in simplest form.
📋 Working Steps — Fill in the blanks!
1
Find the remaining juice after brother's share
Total = 112 ℓ =

Remaining = 32110 =
112 ℓ of orange juice
110
remaining 75
Remaining 75 ℓ split
34 flask
14 drank
Brother (110 ℓ)
Flask (34 of remaining)
Drank (14 of remaining)
2
Find how much Siti drank
Drank = 14 of remaining = 14 × =

Siti drank ℓ of juice.
💡 Hints:
Step 1: Total = 112 = 32 ℓ. Remaining = 32110 = 1510110 = 1410 = 75 ℓ.
Step 2: Drank = 14 × 75 = 720 ℓ.
📐

Area of Triangle VXZ

UWXY is a rectangle and VXZ is a shaded triangle. Find the area of triangle VXZ.
📋 Working Steps — Fill in the blanks!
1
Find the dimensions of rectangle UWXY
From the grid (each square = 1 cm × 1 cm):

Width UW = cm
Height UY = cm

Area of rectangle UWXY = × = cm²
1 cm 1 cm U V W X Y Z
2
Find areas of the 3 surrounding triangles
Subtract 3 triangles from the rectangle:

△UZV: base = UV = cm, height = UZ = cm
Area = ½ × × = cm²

△VWX: base = VW = cm, height = WX = cm
Area = ½ × × = cm²

△ZYX: base = YX = cm, height = YZ = cm
Area = ½ × × = cm²
3
Find area of triangle VXZ
Area of △VXZ = Rectangle − △UZV − △VWX − △ZYX

= = cm²

The area of triangle VXZ is cm².
💡 Hints:
Step 1: Rectangle = 4 cm × 3 cm = 12 cm².
Step 2: △UZV = ½×3×1 = 1.5 cm². △VWX = ½×1×3 = 1.5 cm². △ZYX = ½×4×2 = 4 cm².
Step 3: △VXZ = 12 − 1.5 − 1.5 − 4 = 5 cm².
📐

Shaded Area: Rectangle & Square

The figure is made up of a rectangle and a square.
The length of the rectangle is 24 cm and its breadth is 10 cm.
The side of the square is 7 cm.
What is the area of the shaded part (triangle ABF)?
📋 Working Steps — Fill in the blanks!
10 cm 24 cm 7 cm A B E F G C D
1
Find the height of the shaded triangle
The base of the shaded triangle is AB = side of rectangle = cm

Height of triangle = EF = side of square = cm
2
Find the area of the shaded triangle
Area = ½ × base × height

= ½ × × = cm²

The area of the shaded part is cm².
💡 Hints:
Step 1: Base AB = 24 cm (length of rectangle). Height = BF height = side of square = 7 cm (F is 7 cm below B).
Step 2: Area = ½ × 24 × 7 = 84 cm².
📐

Area of Shaded Figure

Find the area of the shaded figure.
📋 Working Steps — Fill in the blanks!
12 cm 18 cm 20 cm A B C H D G F E
1
Find the total height of each side
GF = CH = HD = cm (equal, shown by tick marks)

Left side AF = AG + GF = 12 + = cm
Right side CE = DE + BC = 18 + = cm
2
Find area of main trapezoid GACEF
Parallel sides: AF = cm, CE = cm, base FE = cm

Area = ½ × ( + ) × = cm²
3
Find areas of triangles ABG and CHD
△ABG: base AB = cm, height AG = cm
Area = ½ × × = cm²

△CHD: base CH = cm, height HD = cm
Area = ½ × × = cm²
4
Find the total shaded area
Total = trapezoid + △ABG + △CHD

= + + = cm²

The area of the shaded figure is cm².
💡 Hints:
Step 1: GF=CH=HD=6 cm. AF=12+6=18 cm. CE=18+6=24 cm.
Step 2: Trapezoid = ½×(18+24)×20 = ½×42×20 = 420 cm².
Step 3: △ABG = ½×20×12 = 120 cm². △CHD = ½×6×6 = 18 cm².
Step 4: Total = 420+120+18 = 558 cm².
📐

Area of Triangle ACE

The figure is made up of two squares, ABFG and CDEF.
GF = 17 cm, FE = 13 cm.
Find the area of triangle ACE.
📋 Working Steps — Fill in the blanks!
17 cm 13 cm A B C D E F G
1
Find BC and the big rectangle
BC = BF − CF = 17 − = cm

Big rectangle (30 × 17):
Area = (GF + FE) × GF = ( + ) × 17 = × 17 = cm²
2
Find the 4 regions outside triangle ACE
△ABC: ½ × AB × BC = ½ × × = cm²

Rect BD: BC × CD = × = cm²

△CDE: ½ × CD × DE = ½ × × = cm²

△AGE: ½ × GE × AG = ½ × × = cm²
3
Find the area of triangle ACE
Area △ACE = Big rect − △ABC − Rect BD − △CDE − △AGE

= = cm²

The area of triangle ACE is cm².
💡 Hints:
Step 1: BC=17−13=4 cm. Big rect=30×17=510 cm².
Step 2: △ABC=½×17×4=34. Rect BD=13×4=52. △CDE=½×13×13=84.5. △AGE=½×30×17=255.
Step 3: △ACE=510−34−52−84.5−255=84.5 cm².
🪣

Water Tank

A rectangular tank 28 cm long, 24 cm wide and 18 cm high was 56 filled with water at first. Mr Lee poured out some water until the height of the water level was 9 cm. Find the volume of water Mr Lee poured out. Give your answer in millilitres.
📋 Working Steps — Fill in the blanks!
18 cm 28 cm 24 cm 9 cm 15 cm
1
Find the initial water height
Initial water height = 56 × 18 cm = cm
2
Find the initial volume of water
Volume = length × width × height

= × × = cm³
3
Find the final volume of water
Volume = × × = cm³
4
Find the volume poured out
Volume poured out = = cm³

Since 1 cm³ = 1 ml:
Mr Lee poured out ml of water.
💡 Hints:
Step 1: 56 × 18 = 15 cm (initial water height).
Step 2: Initial volume = 28×24×15 = 10 080 cm³.
Step 3: Final volume = 28×24×9 = 6 048 cm³.
Step 4: Poured out = 10 080 − 6 048 = 4 032 ml.
📐

Shaded Area in Rectangle

ADEF is a rectangle with area 160 cm². B and C are points on AD. Lines FB, FC, EB and EC are drawn. G is the intersection of FC and EB. The area of triangle CEG is 20 cm². Find the area of the shaded parts.
📋 Working Steps — Fill in the blanks!
Area = 20 cm² A B C D E F G
1
Use symmetry to find △FGB
By symmetry, △FGB ≅ △CEG (congruent triangles).

Area of △FGB = cm²
2
Find areas of △GFE and △FBG
The base and height of △CEF are the same as the length and breadth of the rectangle.
Area of △CEF = ½ × base × height = ½ × length × breadth = ½ × area of rectangle
= ½ × = cm²

G lies on FC, so △CEF = △CGE + △GFE:
Area of △GFE = 80 − = cm²

By symmetry △FBG ≅ △CEG:
Area of △FBG = cm²
3
Find the total shaded area
Shaded area = Area of rectangle − △CGE − △GFE − △FBG

= = cm²

The area of the shaded parts is cm².
💡 Hints:
Step 1: △FBG ≅ △CEG = 20 cm² (by symmetry).
Step 2: △CEF = ½×160 = 80 cm². △GFE = 80−20 = 60 cm². △FBG = 20 cm².
Step 3: Shaded = 160−20−60−20 = 60 cm².
📐

Find the Length of SR

The figure shows rectangle PQRS and right-angled triangle QXR (right angle at X). XR = 3 cm, QX = 4 cm, QR = 5 cm. Find the length of SR.
📋 Working Steps — Fill in the blanks!
4 cm 3 cm 5 cm P X S Q R
1
Find the area of △QXR
Since the right angle is at X, QX and XR are the base and height.

Area of △QXR = 12 × QX × XR
= 12 × × = cm²
2
Find the area of rectangle PQRS
QR, which is the length of the rectangle, can also be the base of △QXR and the corresponding height will be equal to SR which is the breadth of the rectangle.
Therefore, Area of △QXR = 12 × base × height = 12 × length × breadth = 12 × area of rectangle.
Therefore, Area of rectangle = 2 × area of △QXR:

Area of rectangle PQRS = 2 × area of △QXR
= 2 × = cm²
3
Find SR
Area of rectangle = QR × SR
= × SR

SR = ÷ = cm

SR = cm.
💡 Hints:
Step 1: Right angle at X → Area △QXR = 12×4×3 = 6 cm².
Step 2: Area of rectangle = 2 × △QXR = 2×6 = 12 cm².
Step 3: SR = 12 ÷ QR = 12 ÷ 5 = 2.4 cm.
🧊

Painted Cuboid

A cuboid measures 10 cm × 5 cm × 4 cm. Tom painted the whole cuboid.
a) What was the total painted surface area?
b) The cuboid was then cut into 1-cm cubes.
   i. How many cubes had no painted surface?
   ii. How many cubes had exactly 2 painted surfaces?
📋 Working Steps — Fill in the blanks!
🎮 Interactive Cuboid — drag to rotate
10 cm × 5 cm × 4 cm
a
Find the total surface area
A cuboid has 3 pairs of faces:

Top & bottom (10 × 5): 2 × = cm²
Front & back (10 × 4): 2 × = cm²
Left & right (5 × 4): 2 × = cm²

Total surface area = + + = cm²
b i
Cubes with no painted surface
Unpainted cubes are fully inside the cuboid — not touching any face.
Remove 1 cube from each side along every dimension:

Inner length = 10 − 2 =
Inner width  = 5 − 2 =
Inner height = 4 − 2 =

Number of unpainted cubes = × × =
b ii
Cubes with exactly 2 painted surfaces
Cubes with 2 painted faces lie along the edges (not at corners).
A cuboid has 12 edges — 4 of each length.

4 edges of length 10: 4 × (10 − 2) = 4 × =
4 edges of length 5:  4 × (5 − 2) = 4 × =
4 edges of length 4:  4 × (4 − 2) = 4 × =

Total = + + =
💡 Hints:
a) SA = 2(10×5) + 2(10×4) + 2(5×4) = 100+80+40 = 220 cm².
b i) Interior = (10−2)(5−2)(4−2) = 8×3×2 = 48 cubes.
b ii) Edge cubes: 4×8 + 4×3 + 4×2 = 32+12+8 = 52 cubes.