Question
A motorboat covers a certain distance downstream in a
river in 3 hours. It covers the same distance upstream in 3 and a half an hour. If the speed of the water is 1.5km/h, then the speed of the boat in still water is.Solution
. Let the speed of boat in still water =B and speed of stream =S=1.5km/h Downstream speed (B+S) =d/3 D=3(B+S)       … (1) Upstream speed (B-S) =2d /7 D=7/2(B-S)     … (2) Compare both the distance. 3(B+S) = 7/2(B-S) 3B+3S=7B/2-7S/2 6B+6S=7B-7S B=13S B=13×1.5=19.5km/h.
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