Discussion of Question with ID = 068 under Boats-and-Streams

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A boat travels a downstream distance of 84 km in 6 hours, and an upstream distance of 40 km in 4 hours. What is the speed of the stream?


2 kmph.


3 kmph.


4 kmph.


5 kmph.

Ans: a

The downstream speed = $84/6$ = 14 km/h, and the upstream speed = $40/4$ = 10 km/h. By the shortcut method, the speed of the stream is half of the difference between the downstream and upstream speeds of the boat. So the required speed = ${14 - 10}/2$ = 2 km/h.

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