Q:
Mahesh rows to the place 80 km away and back in 20 hours. He finds that he can row 8 km downstream in the same time as 4 km upstream. The speed of the boat in stillwater is
Answer & Explanation
Answer: A) 9 kmph
Explanation: If Mahesh moves 8 km downstream in X hours
Downstream speed = 8/X kmph
upstream speed = 4/X kmph
Now 80/(8/X) + 80/(4/X)=20
X=2/3
downstream Speed = 8/(2/3)= 12 kmph
upstream Speed = 4/(2/3)= 6 kmph
Rate of the stream = (12+6)/2= 9 kmph
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