Multiple choice

Two trains P and Q of length 345 m and 635 m moving in the same direction with a speed of 33 km/hr and 82 km/hr respectively. In what time they cross each other?

  1. 20 sec

  2. 72 sec

  3. 32 sec

  4. 74 sec
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When trains move in the same direction, their relative speed is the difference of their speeds: 82 - 33 = 49 km/hr, which converts to 49 × 5/18 = 245/18 m/s. The total distance to cross is the sum of lengths: 345 + 635 = 980 m. Time = distance / speed = 980 / (245/18) = 72 seconds. Option A (20 sec) would result from incorrectly adding speeds, while C and D are arithmetic errors.

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