SOLUTION: the speed of the boat in still water is 15 miles per hour. it takes the same amount of time for the boat to travel 10 miles downstream as it does to travel 5 miles upstream. find t

Algebra ->  Finance -> SOLUTION: the speed of the boat in still water is 15 miles per hour. it takes the same amount of time for the boat to travel 10 miles downstream as it does to travel 5 miles upstream. find t      Log On


   

Question 1170346: the speed of the boat in still water is 15 miles per hour. it takes the same amount of time for the boat to travel 10 miles downstream as it does to travel 5 miles upstream. find the speed of the current.
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
x=speed of current
15+x downstream and takes 10/(15+x) units are mi/mi/hr or hr
15-x upstream and takes 5/(15-x) hr
Those two are equal because they are both the same time
Cross-multiply, 150-10x =75+5x
75=15x
x=5 mph
downstream and 20 mph and takes 30 min
upstream and 10 mph and takes 30 min