# The boat passed 40 km on a watercourse and 6 km against the current of the river, having spent for all way 3 hours. To find own speed of the boat if the speed of a watercourse of 2 km/h.

Meletiy

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Let x km/h - boat speed, then x +2 km/h - speed on a current x-2 km/h - speed against the current we Work out the equation: 40 / (x +2)+6 / (x-2)=3 of 40 (x-2) of +6 (x+2) of =3 (x+2) (x-2) 40x-80+6x-12=3 (x²-4) 46x-92=3x²-12 3x²-46x+56=0 D=38² x1= (46-38) / (3*2)=1.3 - is impossible - otherwise the boat could not go against the stream, he would stand still h2= (46+38) / (3*2)=14 Answer: 14 km/h

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Mihail

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