Discussion of Question with ID = 055 under Boats-and-Streams

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Question

A steamer boat can travel 560 km downstream in 40 hours. If it covers the same distance upstream in 70 hours, what is the speed of the boat in still water?

A

11 kmph.

B

12 kmph.

C

10 kmph.

D

14 kmph.

Soln.
Ans: a

The downstream speed = $560/40$ = 14 km/h, and the upstream speed = $560/70$ = 8 km/h. By the shortcut method, the speed of the steamer boat in still water is average of its downstream and upstream speeds. So the required speed = ${14 + 8}/2$ = 11 km/h.


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