1.  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 hours
B. 25 hours
C. 35 hours
D. Cannot be determined
E. None of these

Answer: Option C

Explanation:

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

Then, pipes B and C will take :


xandxhours respectively to fill the tank.
24


1 + 2 + 4 = 1
x x x 5

7 = 1
x 5

x = 35 hrs.