Question
The speed of a boat in still water is 10 times the speed
of the stream. If the difference between the upstream and downstream speed of the boats is 20 km/hr, then find the time taken by the boat to travel 180 km in upstream.Solution
Let the speed of the stream be ‘x’ km/hr Therefore, speed of the boat in still water = 10x km/hr Upstream speed of the boat = 10x – x = 9x km/hr Downstream speed of the boat = x + 10x = 11x km/hr According to the question, 11x – 9x = 20 => 2x = 20 => x = 10 Therefore, upstream speed of the boat = 9x = 90 km/hr Required time taken = 180/90 = 2 hours
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