Pipes and Cisterns Practice Test 2 with solutions

Let x, $\frac{\mathit{x}}{2}$ and $\frac{\mathit{x}}{4}$ hours be the time taken by pipes A, B and C respectively to fill the tank, then
$\frac{1}{\mathit{x}}+\frac{2}{\mathit{x}}+\frac{4}{\mathit{x}}$ = $\frac{1}{5}$
⇒ $\frac{7}{\mathit{x}}$ = $\frac{1}{5}$
∴ x = 35 hours.
Hence, time taken by A is 35 hours to fill the tank.