A and B can fill a cistern in 7.5 minutes and 5 minutes respectively and C can carry off 14 litres per minute. If the cistern is already full and all the three pipes are opened, then it is emptied in 1 hr. How may liters can it hold?

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- Dec 20th 2012, 08:10 PMhisajeshPipes and cistern problem. Pleae explain.
A and B can fill a cistern in 7.5 minutes and 5 minutes respectively and C can carry off 14 litres per minute. If the cistern is already full and all the three pipes are opened, then it is emptied in 1 hr. How may liters can it hold?

- Dec 20th 2012, 09:13 PMchiroRe: Pipes and cistern problem. Pleae explain.
Hey hisajesh.

Can you show us any partial attempts you have tried on this problem? (Hint: It will involve derivatives). - Dec 20th 2012, 09:19 PMhisajeshRe: Pipes and cistern problem. Pleae explain.
I took A and B as one pipe which fills 1/3 of the cistern every minute and you have a pipe C emptying 14 liters per minute. The cistern is already full in the begining.

So I took the computation as 1+(1/3)(x)-14 litres=0

so x=3.5 and the total cistern can have 10.5 liters.

But the book answer is 40. Can you help? - Dec 21st 2012, 01:55 AMearbothRe: Pipes and cistern problem. Pleae explain.
- Dec 26th 2012, 08:50 PMibduttRe: Pipes and cistern problem. Pleae explain.