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? Choose the correct choice from the following options.
A) 76 hrs	B) 97 hrs	C) 35 hrs	D) 16 hrs	E) 12 hrs
Suppose pipe A alone takes x hours to fill the tank.   Then, pipes B and C will take x/2 and x/4 hours respectively to fill the tank.   1/x + 2/x + 4/x   = 1/5   7/x = 1/5 =&gt; x = 35 hrs.   Answer: 35 hrs
<result>C</result>
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?