SOLUTION: a boat goes 180 miles downstream in the same time it can go 120 miles upstream the speed is 9 miles per hour find the speed of the boat in still water?

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Question 816589: a boat goes 180 miles downstream in the same time it can go 120 miles upstream the speed is 9 miles per hour find the speed of the boat in still water?
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
boat speed x mph
current speed 9 mph
..
against current x - 9 mph
with current x + 9 mph

Distance against current 120
Distance with current 180
Time = same equate the time against with time with current
t=d/r
120 /(x- 9 )= 180 /(x+ 9 )
120 *(x+ 9 )= 180 *(x- 9 )
120 x + 1080 = 180 x -1620
120 x -180 x = -1620 + -1080
-60 x = -2700
/ -60
x= 45 mph
m.ananth@hotmail.ca