SSC CHSL 5 Aug 2021 Shift 3 Paper

Section: Quantitative Aptitude

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Question : 61 of 100

Marks: +1, -0

The speed of a train is

78 {km} \/ {h}

. If crosses a tunnel in

45 {sec}

and overtakes a person walking at a speed of

6 {km} \/ {h}

, in the same direction, in

15 {sec}

. The length (in

{m}

) of the tunnel is

675
650
975
780

Solution:

Given, speed of train

=78 {km} \/ {h}

=78 × \;{5}/{18}=\;{195}/{9} {m} \/ {s}

Speed of person

=6 {km} \/ {h}

=6 × \;{5}/{18}=\;{5}/{3} {m} \/ {s}

According to the question,

\;{195}/{9}-\;{5}/{3}=\;{\;\text " length of train "\;}/{15}[ ∵ s=\;{d}/{t}]

∴

Length of train

=20 × 15=300 {m}

let the length of the tunnel be

x {m}

.

∴ \;\; 300+x \;\; =\;{195}/{9} × 45=975

x \;\; =975-300=675 {m}

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