Discussion of Question with ID = 080 under Distance-and-Time

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Question

A train passes two persons walking in the same direction as the train. The time it takes to move past the man running at 6km/h is 18sec, whereas the time it takes to cross the other man running at 8km/h is 19sec. What is the speed of the train?

A

44km/h.

B

45km/h.

C

43km/h.

D

46km/h.

Soln.
Ans: a

Let the speed of the train be v km/h. Length of the train calculated with the data for the first man = $(v - 6) × 18$. It should equal the length obtained from the data for the second man. So $(v - 6) × 18$ = $(v - 8) × 19$. Please note that we have not converted seconds to hours because that factor will ultimately cancel away. Solving for v we get 44km/h.


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