NIFT UG 2019 Question Paper with solutions

Question : 19 of 150

Marks: +1, -0

Three taps

A, B

and

C

together can fill an empty cistern in

10 {min}

. The tap

A

alone can fill it in 30 min and the tap

B

alone in 40 min. How long will the tap

C

alone take to fill it?

Solution:

According to the question,
Part of the cistern filled by taps

A

and

B

in 1 min

=1/10

Part of the cistern filled by taps

A

and

B

in 1 min

=\;{1}/{30}+\;{1}/{40}

=\;{4+3}/{120}=\;{7}/{120}

∴

Part of the cistern filled by tap

C

1 {min}

=(A+B+C)-(A+B)

=\;{1}/{10}-\;{7}/{120}=\;{12-7}/{120}=\;{5}/{120}=\;{1}/{24}

Hence, tap

C

will fill the cistern in

24 {min}

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