RRB Group D 17-Sep-2018 Shift 1 Solved Paper

Question : 55 of 100

Marks: +1, -0

Inlet Pipe A can fill a cistern in 32 hours, whereas outlet Pipe

\mathrm{B}

can drain the filled cistern in 40 hours. The two pipes are opened together when the cistern is empty, but the outlet pipe is closed when the cistern is three-quarters full. How many hours will it take in all to fill the cistern?

Validate

Solution:

Cistern filled in one hour by

{A}=\;{1}/{32}

Cistern drained in one hour by

{B}=\;{1}/{40}

Together A and B fill

(\;{1}/{32}-\;{1}/{40})=\;{1}/{160}

Time taken to fill three quarters of cistern by

{A}

and

{B}=160 × \;{3}/{4}=120

hours Now time taken to fill last quarter of cistern
by

{A}=32 × \;{1}/{4}=8

hours

∴

Total time taken

=120+8=128

hours.

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