Q184
ArithmeticSpeed, Time & Distance
A train is 150 m long. It is running at a speed of 41 kmph. A man is running at 11 kmph in the same direction as the train. In what time will it pass the man?
- a.18 seconds
- b.$\frac{3}{10}$ seconds
- c.$\frac{1}{200}$ seconds
- d.$\frac{11}{41}$ seconds
Answer: (A) 18 seconds
Since the man runs in the same direction, relative speed $=41-11=30$ km/h $=30\times\frac{5}{18}=\frac{25}{3}$ m/s. The train passes the man when it covers its own length relative to him: time $=150\div\frac{25}{3}=18$ seconds. Rules: same direction - subtract the speeds; opposite directions - add them; to convert km/h to m/s multiply by $\frac{5}{18}$. Had the man run towards the train, the time would be about 10.4 seconds. The fractional options are absurdly small for a 150 m train.