Question
Two inlet pipes 'C' and 'D' can fill a tank in 18 minutes
and 27 minutes respectively. Both are opened together. After the tank is half full, a leak develops which removes (2/5) of the incoming water. Find the total time to fill the tank.Solution
Let capacity be 162 litres (LCM of 18 and 27)
'C' = 162 ÷ 18 = 9 litres/min
'D' = 162 ÷ 27 = 6 litres/min
Time to fill half = (0.5 × 162) ÷ (9 + 6) = 81 ÷ 15 = 5.4 minutes
Effective rate after leak = (3/5) × (9 + 6) = 9 litres/min
Time to fill remaining = (0.5 × 162) ÷ 9 = 81 ÷ 9 = 9 minutes
Total time = 5.4 + 9 = 14.4 minutes
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