Multiple choice

Two trains can cross a pole in 14 sec. and 16 sec. respectively. Find in how much time will they cross each other if they are coming from the same direction and if the speed of the trains are in the ratio of 7 : 9.

  1. 111 sec

  2. 119 sec.

  3. 131 sec.

  4. 121 sec.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let speeds be 7x and 9x. Lengths are 7x×14 and 9x×16. Relative speed (same direction) = 9x - 7x = 2x. Time = (7x×14 + 9x×16)/(2x) = (98x + 144x)/(2x) = 242x/2x = 121 seconds.

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