Multiple choice

Two trains of lengths 180 metres and 120 metres are running towards each other on parallel tracks. One train is moving at the rate of 65 km/hour and the other is at 55 km/hour. In how many seconds will they cross each other?

  1. 6

  2. 9

  3. 12

  4. 15
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Relative speed = 65 + 55 = 120 km/h = 120 * (5/18) m/s = 100/3 m/s. Total distance = 180 + 120 = 300 m. Time = Distance / Speed = 300 / (100/3) = 900 / 100 = 9 seconds.

AI explanation

To find the time taken for two trains to cross each other, we use the formula time equals the sum of their lengths divided by the sum of their speeds. The total distance to be covered is 180 metres plus 120 metres, which equals 300 metres. Their relative speed is 65 km/hr plus 55 km/hr, equaling 120 km/hr, which converts to 120 multiplied by 5 over 18, giving 100 over 3 metres per second. Dividing the total distance of 300 metres by this relative speed gives 300 multiplied by 3 divided by 100, resulting in a time of 9 seconds.

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