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 choices
A) 35 hrs B) 20 hrs C) 10 hrs D) 15 hrs E) 50 hrs
Pipe 35 hrs alone take x hrs   then pipe B and C will take x/2 and x/4 hrs   =&gt;1/x+2/x+4/x=1/x=&gt;7/x=1/5   x = 35 hrs   35 hrsNSWER 35 hrs
<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?