Give a quick stream of consciousness before answering the following question. A man rows his boat 90 km downstream and 45 km upstream, taking 2 1/2 hours each time. Find the speed of the stream?\nOptions:\n(A) 5 kmph\n(B) 7 kmph\n(C) 9 kmph\n(D) 8 kmph\n(E) 1 kmph
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Speed downstream = d/t = 90/(2 1/2) = 36 kmph\nSpeed upstream = d/t = 45/(2 1/2) = 18 kmph\nThe speed of the stream = (36 - 18)/2 = 9 kmph
The answer: (C).
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