Question 59

Rahul can row a certain distance downstream in 6 hours and return the same distance in 9 hours. If the speed of Rahul in still water is 12 km/h, find the speed of the stream.

Solution

Speed of Rahul = 12 km/hr and let speed of stream = $$x$$ km/hr

=> Downstream speed = $$(12+x)$$ km/hr and Upstream speed = $$(12-x)$$ km/hr

According to ques, since distance in both cases is same and distance = time x speed

=> $$6\times(12+x)=9\times(12-x)$$

=> $$72+6x=108-9x$$

=> $$15x=36$$

=> $$x=\frac{36}{15}=2.4$$

$$\therefore$$ Speed of stream = 2.4 km/hr

=> Ans - (B)

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