Pipes and Cisterns Practice Test 2 with solutions

Question : 20 of 40

Marks: +1, -0

Two pipes P and Q can fill a cistern in 12 and 15 minutes respectively. Both are opened together, but at the end of 3 minutes the first is turned off. How much longer will the cistern take to fill?

$8 1/4$ minutes
$11 1/4$ minutes
$7 1/4$ minutes
$15 1/4$ minutes

Validate

Solution:

In 3 minutes the part filled by both pipes P and Q = 3 ×

(1/{12}+1/{15})

3 × 9/{60}

9/{20}

Remaining part = 1 -

9/{20}

{11}/{20}

Time taken by pipe Q to fill the remaining part =

{{11}/{20}}/{1/{15}}

{33}/4

8 1/4

min.

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