A boy can swim in still water at 4.5 kmh, but takes twice as long to swim upstream than downstream. The speed of the stream is - www.mathselab.com

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 ?

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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