Question
The speed of current is 8 km/h. What will be the
respective downstream speed and upstream speed of a boy rowing a boat, if one fifth 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 = 8 km/h Downstream speed = (X + 8) km/h Upstream speed = (X – 8) km/h Let time be ‘t’ hours. ⇒ [(X + 8) t]/5 = (X – 8) t ⇒ X + 8 = 5X – 40 ⇒ X = 12 km/h Downstream speed = 12 + 8 = 20 km/h Upstream speed = 12 – 8 = 4 km/h
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