Question

A tank is filled in 5 hours by three pipes A, B and C. The pipe C is twice, as fast as B and B is twice as fast as A. How much time will pipe A alone take to fill the tank?

• A. 20 hrs
• B. 35 hrs
• C. Cannot be determined
• D. None of these

Answer 1

The correct option is B

35 hrs

Suppose pipe A alone takes x hours to fill the tank.

Then, pipes B and C will take $\frac{x}{2}and\frac{x}{4}$ hours respectively to fill the tank.

$\therefore \frac{1}{x}+\frac{2}{x}+\frac{4}{x}=\frac{1}{5}\iff \frac{7}{x}=\frac{1}{5}\iff x=35hours$