Quantitative Aptitude – TSD – Two persons are walking beside a railway track at respective


Slot – 1 – Quantitative Aptitude – TSD – Two persons are walking beside a railway track at respective


Q. 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?
  1. 87
  2. 82
  3. 75
  4. 78

Answer: 82

Solution:
Let the length of train = l and speed = x then
l/(x-2) = 90
l = 90(x-2)
similarly l = 100(x-4)
on solving 90(x-2) = 100(x-4)
x = 22
l = 90(x-2) = 1800
time taken to cross the pole = l/x = 1800/22 = 81.81 = 82 (approx)


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