Question
The speed of a boat in still water is 12 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 220 km in upstream.Solution
Let the speed of the stream be ‘x’ km/hr Therefore, speed of the boat in still water = 12x km/hr Upstream speed of the boat = 12x – x = 11x km/hr Downstream speed of the boat = x + 12x = 13x km/hr According to the question, 13x – 11x = 20 => 2x = 20 => x = 10 Therefore, upstream speed of the boat = 11x = 110 km/hr Required time taken = 220/110 = 2 hours
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