RRB Paramedical Staff Nurse Model Paper 4

Question : 45 of 100

Marks: +1, -0

A cistern can be filled with water by a pipe in 5 h and it can be emptied by a second pipe in 4 h. If both the pipes are opened when the cistern is full, the time in which it will be emptied is

9 h
18 h
20 h
$20{1/2}$ h

Validate

Solution:

According to the question, Cistern can be filled by pipe in

1 {h}=\;{1}/{5}

part
Cistern can be emptied in

1{h}=\;{1}/{4}

part
When both the pipes are opened, simultaneously,
Cistern can be emptied in 1h

=\;{1}/{4}-\;{1}/{5}

=\;{5-4}/{20}

=\;{1}/{20}

part
Thus, time in which it will be emptied

=20 {h}

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