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 answers:
A) 35 hours
B) 25 hours
C) 20 Hours
D) Cannot be determined
E) None of these
Let pipe A alone takes to fill the tank = x hours.   Then, pipes B take twice fast as A = x/2   And pipes C take twice fast as B = x/4   Therefore, Tank filled in 5 hours by A,B,C pipes =&gt; 1/x + 2/x + 4/x = 1/5   ==&gt; 7/x = 1/5   ==&gt; x = 5*7= 
<gadget id="calculator">5*7</gadget>
<output>35</output>
35 hours   x= 35 hrs.   35 hoursNSWER:35 hours
<result>A</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?