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?
20 hours
25 hours
35 hours
Cannot be determined
Explanation:
Suppose pipe A alone takes $ x $ hours to fill the tank.
Then, pipes B and C will take$ \dfrac{x}{2} $and$ \dfrac{x}{4} $hours respectively to fill the tank.
$\therefore \dfrac{1}{x} $+$ \dfrac{2}{x} $+$ \dfrac{4}{x} $=$ \dfrac{1}{5} $
$\Rightarrow \dfrac{7}{x} $=$ \dfrac{1}{5} $
$\Rightarrow x $ = 35 hrs.