Question 67

A tap can empty a tank in 30 minutes. A second tap can empty it in 45 minutes. If both the taps operate simultaneously, how much time is needed to empty the tank ?

Solution

Let the volume of tank be 90 litres.

1st tap empty it in 30 min

=> Rate of 1st tap = $$\frac{90}{30}$$ = 3 $$l/min$$

2nd tap can empty it in 45 minutes.

=> Rate of 2nd tap = $$\frac{90}{45}$$ = 2 $$l/min$$

Rate at which both taps empty it = 3+2 = 5 $$l/min$$

=> Time needed to empty tank = $$\frac{90}{5}$$ = 18 min

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