Question 56

Pipe A can fill a tank in 6 hours. Pipe B can fill the same tank in 8 hours. Pipe A, B and C together can fill the same tank in 12 hours. Then which of the following statements is true for pipe C?

Solution

Pipe A, B and C together can fill the same tank in 12 hours.

Let C fill the tank in c hours.

$$\frac{1}{6} + \frac{1}{8} + \frac{1}{c} = \frac{1}{12}$$

$$\frac{1}{c} = \frac{1}{12} - \frac{7}{24} = \frac{-5}{24} $$

Since it is negative , instead of filling C will empty the tank.

C takes $$\frac{24}{5} = 4.8 hrs $$

So, the answer would be option c)It can empty the tank in 4 hours 48 minutes.

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