Question

Three pipes a, b and c can fill a cistern in 6 hours. After working at it together for 2 hours, c is closed and a and b can fill the remaining part in 7 hours. The number of hours taken by c alone to fill the cistern is:

Answer 1

A+B+C Can fill cistern in 1 hour =1/6 part

and in 2 hrs =2/6 part =1/3 part

Remaining 2/3 part filled by A+B in 7 hrs

And 1 part filled by A+B in (7×3)/2=21/2 hr

In 1 hr 2/21 part will be filled by A+B

In 1 hr C will fill ( 1/6 -2/21) part

ie. C will fill (7 -4)/42 =3/42=1/14 part in 1 hr

ie. C will fill 1 part(full) in 14 hours