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?
Choices:
A) 15 hours	B) 18 hours	C) 20 hours	D) 25 hours	E) 35 hours
Let A fill tank in x hrs.   Therefore tank filled in one hrs is 1/x.   And B pipe is twice than A means 2 (1/x).   C pipe is twice than B means 2 (2 (1/x) ) i.e 4/x.   1/x+2/x+4/x = 1/5.   7/x = 1/5.   x = 35 hrs.   ANSW35 hoursR :e
<result>E</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?