Question
A boy can swim in still water at 4.5 km/h, but takes twice as long to swim upstream than downstream. The speed of the stream is ?
A. 1.5 kmph
B. 1.8 kmph
C. 2 kmph
D. 2.2 kmph
Answer: A. 1.5 kmph
Solution:
Speed of Boy is B = 4.5 kmph
Let the speed of the stream is S = x kmph
Then speed in Down Stream = 4.5 + x
speed in Up Stream = 4.5 – x
As the distance is same,
=> 4.5 + x = (4.5 – x) 2
=> 4.5 + x = 9 -2x
3x = 4.5
x = 1.5 kmph
Hence, The Answer is 1.5 kmph.
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