Question
A motor boat covers a certain distance downstream in a
river in 4 hours. It covers the same distance upstream in 4 hours and 30 minutes. If the speed of water is 2 km/h, then the speed of the boat in still water is:Solution
Let the speed of boat in still water be x km/hr and the distance be y km. Rate downstream = (x + 2) km/hr Rate upstream = (x – 2) km/hr According to the question, y/(x + 2) = 4 --- (i) y/(x – 2) = 9/2 --- (ii) On dividing equation (i) by (ii), (x – 2)/(x + 2) = 4/(9/2) = 8/9 9x – 18 = 8x + 16 x = 18 + 16 = 34 kmph
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