Multiple choice

Two trains each 250 m in length are running on the same parallel lines in opposite directions with the speed of 80 kmph and 70 kmph respectively. In what time will they cross each other completely?

  1. 10 sec

  2. 12 sec

  3. 11 sec

  4. 14sec
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Total length = 250 + 250 = 500 m = 0.5 km. Relative speed = 80 + 70 = 150 km/h. Time = 0.5 / 150 hours = (1/300) * 3600 seconds = 12 seconds.

AI explanation

When two trains run in opposite directions, their relative speed is the sum of their individual speeds: 80 kmph + 70 kmph = 150 kmph. Convert this relative speed to m/sec by multiplying by 5/18, which gives 150 * 5/18 = 125/3 m/sec. The total distance to be covered is the sum of their lengths, which is 250 m + 250 m = 500 m. The time to cross each other completely is the total distance divided by the relative speed: 500 / (125/3) = 12 sec.

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