Question

pipe A can fill a cistern in 10 hours and pipe B can empty the filled cistern in 15 hours. if both the pipes are opened together in cistern then in how much time cistern will be filled

Answer 1

Given pipe A can fill the cistern in 10 hours.
Cistern filled by pipeA in 1 hour = 1/10
Pipe B can fill the cistern in 15hrs
In 1 hour = 1/15
Let the cistern filled by both the pipes be in 1/x hrs.
so according to the question :
1/10 + 1/15 = 1/x
Take L.C.M = 30
3/30 + 2 / 30 = 1/x
5/30 = 1/x
On cross multiplying we get :
5x = 30
x = 6
So both the pipes together can fill the cisteen in 6 hours respectively.

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