# A person can row a boat at the rate of 5km/hr in still water. He takes thrice as much time in going 40km upstream as in going 40 km downstream. Find the speed of the stream.

Given, speed of the boat in still water = 5 km/hr

Let's assume the speed of the stream = k km/hr

Speed of the boat upstream = (5 – k) km/hr

Speed of the boat downstream = (5 + k) km/hr

Time to cover 40 km upstream = 3 × Time to cover 40 km downstream

40/(5-k) = 3x40/(5+k)

3x(5-k) = 5+k

4k = 10

Speed of the stream k = 2.5 km/hr.

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