Multiple choice

A $210$ m long train takes $6$ s to cross a man running at $9$ kmph in a direction opposite to that of the train. What is the speed of the train ? (in kmph)

  1. $127$
  2. $121$
  3. $117$
  4. $108$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Relative speed = 210m / 6s = 35 m/s. 35 m/s = 35 * 18/5 = 126 kmph. Since they are moving in opposite directions, relative speed = speed of train + speed of man. 126 = speed of train + 9, so speed of train = 117 kmph.