Question

The speed of a boat in still water is 5 km/h. If
it takes thrice as much time in going 20 km
upstream as in going the same distance
downstream find the speed of the stream.
(a) 2.5 km/h (b) 5.5 km/h (c) 4.5 km/h (d) 3.5 km/h
beed of boat in still wotor - Elemi​

Answer 1

Man's speed with the current = 15 km/hr

=> speed of the man + speed of the current = 15 km/hr

speed of the current is 2.5 km/hr

Hence, speed of the man = 15 - 2.5 = 12.5 km/hr

man's speed against the current = speed of the man - speed of the current

= 12.5 - 2.5 = 10 km/hr

therefore option B

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