Question 3

It takes 6 hours for pump A, used alone, to fill a tank of water. Pump B alone takes 8 hours to fill the same tank. A, B and another pump C all together fill the tank in 2 hours. How long would pump C take, used alone, to fill the tank?

Solution

Assuming tank volume to be 48 litres,

Flow rate through pump A = 48/6 = 8 litres/hr

Flow rate through pump B = 48/8 = 6 litres/hr

Flow rate through pumps A, B, C together = 48/2 = 24 litres/hr

So, flow rate of pump C alone = 24 - (8+6) = 10 litres/hr

$$\therefore\ $$ Time taken by C alone to fill the tank = 48/10 = 4.8 hrs

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