Two pipes can fill a tank in 18 minutes and 36 minutes. A waste pipe removes 5 litres per minute. With all three open, the tank fills in 16 minutes. What is the capacity of the tank?
Correct answer A. 240 litres
Explanation
Waste rate = 1/18 + 1/36 − 1/16 = 1/12 − 1/16 = 1/48 of the tank per minute. That equals 5 litres, so capacity = 48 × 5 = 240 litres.
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