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?
Printable View
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?
Hey hisajesh.
Can you show us any partial attempts you have tried on this problem? (Hint: It will involve derivatives).
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?
1. Let V be the volume of the cistern.Quote:
Originally Posted by hisajesh
2. A and B add 1/3 of V to the filled cistern while C take 14 liters per minute from the cistern. After 1 h = 60 min the cistern is empty:
V + (1/3) V* 60 - 14 * 60 = 0
3. Solve for V.
Attachment 26368
Quote:
Originally Posted by hisajesh
