Tank P and Tank Q are rectangular containers.
- Tank Q measures 50 cm long, 40 cm wide and 20 cm high. It is 34 full of water. What is the volume of water in Tank Q?
- Tank P is 12 full of water. After all the water from Tank Q is poured into Tank P, Tank P is 45 full. The base area of Tank P is 5000 cm². Find the height of Tank P.
Need a hint?
In (b), the water poured in fills the gap between 12 full and 45 full. What fraction of Tank P is that? Use it to find the whole volume first.
Worked answer
- (a) Volume of Tank Q = 50 × 40 × 20 = 40000 cm³
- Volume of water = 34 × 40000 = 30000 cm³
- (b) 45 − 12 = 310 of Tank P is filled by the water from Tank Q
- 310 of Tank P's volume = 30000 cm³
- Volume of Tank P = 30000 ÷ 3 × 10 = 100000 cm³
- Height of Tank P = 100000 ÷ 5000 = 20 cm
The mistake this question tests
Fraction of a remainder
A common mistake is to divide 30000 cm³ by the base area 5000 cm² to get 6 cm and call that the height of Tank P. That 6 cm is only the rise in water level, not the height of the whole tank.
How to fix it at home →Wrong answers children often give:
- 6 Calculation slip
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See the answer →Practise PSLE area & volume until the mistakes stop.
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