a stream flows from A to B a distance of 30 km at the rate of 2km/h and a man can row up and down in 8 hours.find the speed of the man in still watet.
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Answer:
8km/h
Step-by-step explanation:
Let the speed of man in still water be 'x'.
Distance = 30km
Speed of stream = 2km/h
Speed = Dist./Time
Time = Dist./speed
8hrs. = 30/x-2 + 30/x+2
8 = 30x + 60 + 30x - 60/x^2 - 4
8x^2 - 32 = 60x
0 = 8x^2 - 60x - 32
0 = 2x^2 - 15x - 8
0 = 2x^2 +x - 16x - 8
0 = x(2x + 1) - 8 (2x+1)
0 = (2x+1)(x-8)
x = -1/2 ; x = 8
As speed can't be negative,
x = 8km/h.
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