Multiple choice

Train A left the station at 11:30 a.m. and is travelling at speed of 80 kmph. Train B left the station after 45 min and is travelling on parallel track in the same direction at speed of 120 kmph. At what time will train B cross train A?

  1. 1:00 p.m.

  2. 1:15 p.m.

  3. 1:45 p.m.

  4. 2:05 p.m.

  5. 2:20 p.m.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Train A travels for 45 minutes (0.75 hours) before B starts. Distance A = 80 * 0.75 = 60 km. Relative speed = 120 - 80 = 40 kmph. Time for B to catch A = 60 / 40 = 1.5 hours (1 hour 30 min). Train B starts at 12:15 p.m. (11:30 + 45 min). 12:15 + 1:30 = 1:45 p.m.

AI explanation

By the time train B starts, train A has travelled for 45 minutes at 80 kmph, covering a relative distance of 60 kilometers. The relative speed of train B with respect to train A is 120 kmph minus 80 kmph, which equals 40 kmph. Using the formula time equals distance divided by relative speed, train B will take 60 divided by 40, which is 1.5 hours or 1 hour and 30 minutes, after its 12:15 p.m. departure. Adding this time gives a crossing time of 1:45 p.m.

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