KJSEA 2025 Maths Q11 — Capacity of a Cuboid Milk Packet

KJSEA 2025 Grade 9 Measurement

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The Question

“A packet of milk is a cuboid. Its length is 8.5 cm, its width is 5 cm, and its height is 12 cm. What is the capacity of the packet in litres?”

1

Understand what capacity means

Capacity tells us how much liquid a container can hold, and for a solid shape it equals the volume of that shape. Because the milk packet is a cuboid, we can find its volume by multiplying the three dimensions together, so start by recalling that formula.

V=length×width×heightV = \text{length} \times \text{width} \times \text{height}
2

Multiply the three dimensions

Put the given numbers into the formula. It is easiest to multiply the length by the width first, then multiply that result by the height. Working in this order keeps the arithmetic simple and gives the volume in cubic centimetres because every measurement was in centimetres.

V=8.5×5×12V = 8.5 \times 5 \times 12
8.5×5=42.58.5 \times 5 = 42.5
42.5×12=510 cm342.5 \times 12 = 510 \text{ cm}^{3}
3

Convert cubic centimetres to litres

The question asks for the answer in litres, not cubic centimetres, so we must convert. There are 1000 cubic centimetres in one litre, which means we divide the volume by 1000 to change the unit. Dividing by 1000 simply moves the decimal point three places to the left.

1 L=1000 cm31 \text{ L} = 1000 \text{ cm}^{3}
V=510÷1000=0.51 LV = 510 \div 1000 = 0.51 \text{ L}

Dividing by 1000 shifts 510 to 0.510, which is 0.51 litres.

Final Result

The capacity of the milk packet is 0.51 litres, which is option A.

Why this method works

The method works because capacity and volume measure the same thing for a container, and a cuboid's volume is the amount of space enclosed by its length, width, and height multiplied together. Multiplying centimetre lengths gives cubic centimetres, a unit of volume. Since a litre is defined as exactly 1000 cubic centimetres, dividing the cubic-centimetre volume by 1000 rescales the same quantity into litres without changing how much liquid it represents.

✓

Multiply back: 0.51 L times 1000 gives 510 cubic centimetres, matching the volume we found.