CAT 2020 Exam Shift 1 Solved Paper

Question : 56 of 76

Marks: +1, -0

Two persons are walking beside a railway track at respective speeds of 2 and

4 {\km}

per hour in the same direction. A train came from behind them and crossed them in 90 and 100 seconds, respectively. The time, in seconds, taken by the train to cross an electric post is nearest to

Validate

Solution:

Let the length of the train be I and its speed bes. Given

\;{l}/{(s-2) × \;{5}/{18}}=90 ; \;{l}/{(s-4) × \;{5}/{18}}=100

⇒ 90(s-2) × \;{5}/{18}=100(s-4) × \;{5}/{18} ⇒ s=22

∴

Length of the train

=500 {m}

.
Hence the required time to cross a lamp post

=\;{500}/{22 × \;{5}/{18}}

i.e., 81.81 (or) 82 sec.

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