Question
Pipes 'G' and 'H' can fill a tank in 15 and 20 minutes
respectively. A leak opens when the tank is half full, removing (2/7)th of the water supplied. What is the total time to fill the tank?Solution
Capacity = 60 litres (LCM of 15 and 20)
'G' = 60 ÷ 15 = 4 litres/min
'H' = 60 ÷ 20 = 3 litres/min
Time to fill half = 30 ÷ (4 + 3) = 30 ÷ 7 = 4.29 minutes
Effective rate = (5/7) × 7 = 5 litres/min
Time to fill remaining = 30 ÷ 5 = 6 minutes
Total time = 4.29 + 6 = 10.29 minutes
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