Question
A boat takes 4 hours to travel 36 km downstream and 9 hours to travel the same distance upstream. Find the speed of the boat in still water and the speed of the stream.
Solution
ATQ, Let boat speed in still water = b km/h Stream speed = s km/h Downstream speed = b + s = 36/4 = 9 Upstream speed = b − s = 36/9 = 4 Solve: b + s = 9 b − s = 4 Add: 2b = 13 ⇒ b = 6.5 km/h Then s = 9 − 6.5 = 2.5 km/h Answer: Boat speed = 6.5 km/h, Stream speed = 2.5 km/h.
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