Problem 15 · 2015 Math Kangaroo
Medium
Ratios, Rates & Proportions
unit-rateproportion
During a thunderstorm it rained 15 litres per square metre. By how much did the water level of an outdoor swimming pool increase?
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Answer: D — 1.5 cm
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Hint 1 of 2
Rain depth does not depend on the pool's area: a fixed litres-per-square-metre is a fixed depth.
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Hint 2 of 2
1 litre spread over 1 square metre is a layer 1 mm deep.
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Approach: litres per square metre is a depth
- A volume of 1 litre spread over 1 square metre gives a layer 1 mm deep.
- So 15 litres per square metre is 15 mm deep.
- 15 mm = 1.5 cm, the same for any pool size.
- So the water level rose 1.5 cm (D).
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