Farid stores his model railway in a rectangular cardboard box. The box has a square end face with an area of 64 cm², and its length is 20 cm. What is the volume of the box?
- 64 cm³
- 160 cm³
- 1280 cm³
- 10 240 cm³
Need a hint?
The end face is a square. Find two equal side lengths whose product is 64, then use the face area to calculate the volume.
Worked answer
- The square face has side length 8 cm because 8 × 8 = 64.
- Volume = area of square face × length = 64 × 20 = 1280 cm³.
Answer: 1280 cm³
The mistake this question tests
Habit
Area and perimeter formulas
Some pupils find the 8 cm side and multiply 8 × 20, forgetting that the square face has two sides of 8 cm.
How to fix it at home →Wrong answers children often give:
- 64 cm³ Left out the units
- 160 cm³ Area and perimeter formulas
- 10 240 cm³ Area and perimeter formulas
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See the answer →Practise PSLE area & volume until the mistakes stop.
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