SOLUTION: the speed of a boat in still water is 16 km/h.The boat travels 43 km upstream and 45 km downstream in a total time of 20 hr.what is the speed of the stream?
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Question 384264: the speed of a boat in still water is 16 km/h.The boat travels 43 km upstream and 45 km downstream in a total time of 20 hr.what is the speed of the stream?
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
the speed of a boat in still water is 16 km/h.The boat travels 43 km upstream and 45 km downstream in a total time of 20 hr.what is the speed of the stream?
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speed of boat = 16km/h
speed of current = x km/h
..
upstream speed = 16-x
downstream speed = 16+x
..
d upstream = 43 km
d downstream = 45 km
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43/(16-x)+45/(16+x)= 20
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LCD = (16+x)(16-x)
43(16+x)+45(16-x)/(16+x)(16-x)=20
688+43x+720-45x/16+x)(16-x)=20
1408-2x=20(256-x^2)
1408-2x=5120-20x^2
20x^2-2x=5120-1408
20x^2-2x=3712
20x^2-2x-3712=0
..
solve for roots x1 & x2 using quadratic equation
discriminant =296964
x1= 13.7 km/h the speed of current.
x2 will be negative so ignore.
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13.7 km/h the speed of current.
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m.ananth@hotmail.ca
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