A cistern has 3 pipes A, B and C, A and B can fill it in 2 and 3 hours respectively. C is a waste pipe. If all the 3 pipes be opened at once, 7/24 of the cistern will be filled up in 30 minutes. In what time can C empty the full cistern?

Question

Accepted Answer

∵ 7/24 of the cistern will be filled up in 1/2 hr.
∴ The whole of the cistern will be filled up in (1/2) x (24/7) = 12/7 hrs.
Let the pipe C be empty the whole cistern in h hours
Now, applying the given rule we have,
(2 x 3 x h) / (3 x h + 2 x h - 2 x 3) = 12/7
or 42h = 60h - 72
∴ h = 4 hours.

A cistern has 3 pipes A, B and C, A and B can fill it in 2 and 3 hours respectively. C is a waste pipe. If all the 3 pipes be opened at once, 7/24 of the cistern will be filled up in 30 minutes. In what time can C empty the full cistern?

Discussion & Comments