A tank is filled in 10 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 option:
A) 70 hours  B) 30 hours  C) 35 hours  D) 50 hours  E) 60 hours
1/A + 1/B + 1/C = 1/10 ( a, b and c 1 hour work)   given.. 1/B= 2/A and 1/C = 2/B = 4/A   hence 1/A + 2/A + 4/A = 1/10   on solving.... we get 1/70 hours = 1/70 ( work done by 70 hours in 1 hour)   therefore time taken by 70 hours is 70 hours to finish the whole work   70 hoursNSWER:70 hours
<result>A</result>
A tank is filled in 10 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?