SOLUTION: The speed of a stream is 5mph. A boat travels 5 miles upstream in the same time it takes to travel 15 miles downstream. What is the speed of the boat in still water. help

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Question 428009: The speed of a stream is 5mph. A boat travels 5 miles upstream in the same time it takes to travel 15 miles downstream. What is the speed of the boat in still water.



help please.
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
boat speed x mph
current speed 5 mph
..
against current x - 5 mph
with current x + 5 mph

Distance against current 5
Distance with current 15
Time = same
5 /(x- 3 )= 15 /(x+ 3 )
5 *(x+ 3 )= 15 *(x- 3 )
5 x + 15 = 15 x -45
15 x -5 x = 45 + 15
10 x = 60
/ 10
x= 6 mph