RRB Group D 15-Sep-2018 Shift 1 Solved Paper

Question : 63 of 100

Marks: +1, -0

One pipe can fill an empty cistern in 7.8 hours while another can drain the cistern full in 19.5 hours. Both the pipes were turned on when the cistern was half-empty. How long will it take for the cistern to be full?

6.5 hours
7.8 hours
3.9 hours
5.2 hours

Validate

Solution:

A can fill the cistern in 7.8 hours

{B}

can empty the cistern in 19.5 hours

∴ A+B

can fill the cistern in

=\;{7.8 × 19.5}/{19.5-7.8}=\;{152.1}/{11.7}=13 \;\text " hours "\;

since cistern was already half full

∴

Actual time taken to fillthe half filled cistern

=\;{13}/{2}=6.5

hours

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