Question 48

Two pipes P and Q can fill a tank in 32 minutes and 48 minutes. Both pipes are opened and after some time pipe Q is turned off. The tank is filled in 24 minutes. When was the pipe Q closed?

Solution

Let say, after x min Pipe Q turned off.

P and Q together can fill in 1 min =

(1/32)+(1/48)=(3+2)/96=5/96.

So, in x min they will fill =5x/96 part.

But, (24-x) min ,P can fill =(24-x)/32.

So, (5x/96)+(24-x)/32=1.

or,(5x+72-3x)/96=1.

or, 2x+72=96.

or, x=12.

So, D is correct choice.

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