Question 44

A boatman rows to a place 45 km distant and back in 20 hours. He finds that he can row 12 km with the stream in same time as 4 km against the stream . Find the speed of the stream.

Solution

Let the speed of the boat be u and that of stream be v.

12/u+v = 3/u-v

4u - 4v = u + v

3u = 5v

45/u+v + 45/u-v = 20

Putting value of u in above equation and solving, we get

v = 3 km/hr [speed of stream]

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