Vishal rows to a place 36 km distance and back in 21 2 hours He finds that he can row 4km with the s...........

Quantitative Aptitude (CDS) Boats and Streams

Vishal rows to a place 36 km distance and back in 21/2 hours. He finds that he can row 4km with the stream at the same time as 3km against the stream. The rate of the stream is?

0.5kmph

2kmph

1.5kmph

1kmph

Explanation:

Suppose he moves 4 km downstream in x hours. Then,
Speed downsteam = (4/x)kmph,
speed upstream = (2/x)kmph
36/(5/x) + 36(4/x) = 21/2
x = 126/252
x = 1/2
So speed dowmstream = 8kmph, speed upstream = 6kmph
Rate of the stream = 1/2(8-6)kmph
= 1kmph

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