Question
The speed of a boat in still water is 7.5 times the
speed of the stream. If the difference between the upstream and downstream speed of the boats is 40 km/hr, then find the time taken by the boat to travel 260 km in upstream.Solution
Let the speed of the stream be ‘x’ km/hr Therefore, speed of the boat in still water = 7.5x km/hr Upstream speed of the boat = 7.5x – x = 6.5x km/hr Downstream speed of the boat = x + 7.5x = 8.5x km/hr According to the question, 8.5x – 6.5x = 40 => 2x = 40 => x = 20 Therefore, upstream speed of the boat = 6.5x = 130 km/hr Required time taken = 260/130 = 2 hours
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