91.
A train 110 meters long is running with a speed of 60 kmph. In what time will it pass a man who is running at 6 kmph in the direction opposite to that in which the train is going?
Answer: B
The man walks toward the train, so the speeds add.
\[ \text{relative speed} = 60 + 6 = 66 \text{ kmph} = 66 \times \frac{5}{18} = \frac{55}{3} \text{ m/s} \]
A man is a point, so only the train's own length is covered:
\[ t = \frac{110 \times 3}{55} = 6 \text{ seconds} \]
Had he walked the same way as the train, the relative speed would be 54 kmph and the answer about 7.3 seconds.
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