Question

A man can row at 6 km/h in still water and at 4 km/h upstream. how long will the man take to go to a place 1 km downstream and return?


a.36 min


b.24 min


c.12 min


d.18min

Answer 1

Solution :-


speed of man in still water = 6 km/h

let the speed of river = v km/h

speed of man upstream = (6-v) km/h = 4 km/h

thus v = (6-4) km/h = 2 km/h

speed of the man downstream = (6+v) = (6+2) km/h = 8 km/h

to go 1 km downstream, time = 1/8 hour

to return 1 km upstream, time = 1/4 hour

total time = 1/8 + 1/4 = (2+1)/8 = 3/8 hours

So he will take 3/8 hours to go to a place 1 km downstream and return.

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