SSC CGL 16 Aug 2015 Shift 2 Paper

Question : 144 of 200

Marks: +1, -0

Two pipes A and B can fill a tank with water in 30 minutes and 45 minutes respectively. The water pipe C can empty the tank in 36 minutes. First A and B are opened. After 12 minutes C is opened. Total time (in minutes) in which the tank will be filled up is :

Validate

Solution:

Part of tank filled by pipes A and B in 1 minute
=

1/{30}+1/{45}

{3+2}/{90}

1/{18}

part
∴ Part of tank filled in 12 minutes
=

{12}/{18}

2/3

part
Remaining part
= 1 -

2/3

1/3

part
When pipe C is opened,
Part of tank filled by all three pipes =

1/{30}+1/{45}-1/{36}

{6+4-5}/{180}

5/{180}

1/{36}

∴ Time taken in filling

1/3

part
=

1/3

× 36 = 12 minutes
∴ Total time = 12 + 12
= 24 minutes

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