Question
Covering 54 km upstream and 150 km downstream takes a
boat 8 hours in total. The boat’s still-water speed is 18 km/h more than the stream. What is the stream speed?Solution
Let the speed of the stream = x And the speed of the boat in still water = x + 18 54/(x + 18 − x) + 150/(x + 18 + x) = 8 54/18 + 150/(2x + 18) = 8 3 + 150/(2x + 18) = 8 150/(2x + 18) = 5 2x + 18 = 150/5 2x + 18 = 30 2x = 12 x = 6 The speed of the stream = 6 km/hr
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