NIMCET 2018 Question Paper with solutions

Question : 74 of 120

Marks: +1, -0

Two pipes A and B can fill a cistern in 37.5 min and 46 min, respectively. Both pipes are opened. The cistern will be filled in just half an hour, if Hie pipe B is turned off after

6 min
9 min
10 min
15 min

Validate

Solution:

Pipe A can fill a cistern in 37.5 min
∴ Part of cistern filled by pipe A in 1 min =

1/{37.5}

Similarly, part of cistern filled by pipe B in 1 min =

1/{45}

Now, the cistern will be filled in half an hour if pipe Bis turned off after some time.
Let pipe Bis turned off after x min.
∴

{30}/{37.5}+x/{45}

= 1
0.8 +

x/{45}

= 1
x = 45 × 0.2 = 9 min

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