Question
The speed of current is 9 km/h. What will be the
respective downstream speed and upstream speed of a boy rowing a boat, if one seventh of the distance covered going downstream in a certain time is equal to the distance covered going upstream in the same time?Solution
Let the speed of boy in still water be X km/h. And the speed of current = 9 km/h Downstream speed = (X + 9) km/h Upstream speed = (X – 9) km/h Let time be ‘t’ hours. ⇒ [(X + 9) t]/7 = (X – 9) t ⇒ X + 9 = 7X – 63 ⇒ X = 12 km/h Downstream speed = 12 + 9 = 21 km/h Upstream speed = 12 – 9 = 3 km/h
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