SOLUTION: John’s boat travels 7 km/hour in still water. He travels 45 km upstream and 45 km downstream in a total time of 14 hours. What is the speed of the river?

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Question 857644: John’s boat travels 7 km/hour in still water. He travels 45 km upstream and
45 km downstream in a total time of 14 hours. What is the speed of the river?
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
boat speed = 7 km/h
current speed = x km/h

against current = 7 - x
with current = 7 + x

Total distance = 45 miles Total Time= 14.00 hours
Time upstream + time downstream = 14 hours

45 /( 7 - x )+ 45 /( 7 + x )= 14
45 ( 7 + x )+ 45 ( 7 - x )= 14.00 ( 49 - 1 X^2 )
315 + 45 x + 315 -45 x = 686 - 14 X^2
630 - -686 = -14 X^2
-56 = -14 X^2
-14 X^2= -56
X^2 = 4
X = +/- 2
speed of boat = 2km/h