SOLUTION: The speed of a boat in still water is 5 miles per hour. If the boat travels 3 miles downstream in the same amount of time it takes to travel 1.5 miles upstream, what is the speed o

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Question 419037: The speed of a boat in still water is 5 miles per hour. If the boat travels 3 miles downstream in the same amount of time it takes to travel 1.5 miles upstream, what is the speed of the current?
Found 2 solutions by mananth, ikleyn:
Answer by mananth(16949) About Me  (Show Source):
You can put this solution on YOUR website!
boat speed = 5 mph
current speed = x mph

Speed upstream= 5 - x
Speed downstream= 5 + x

Distance upstream= 1.5 miles
Distance downstream= 3 miles

t=d/r time upstream = time downstream
1.5 / ( 5 - x )= 3 / ( 5 + x )
1.5 ( 5 + x )= 3 ( 5 -x )
7.5 + 1.5 x = 15 - 3 x
3 x -1.5 x = 7.5
1.5 x = 7.5
/ 1.5
x = 5 mph boat speed

Answer by ikleyn(53427) About Me  (Show Source):
You can put this solution on YOUR website!
.
The speed of a boat in still water is 5 miles per hour. If the boat travels 3 miles downstream
in the same amount of time it takes to travel 1.5 miles upstream, what is the speed of the current?
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        The solution and the answer in the post by @mananth both are incorrect.
        I came to bring a correct solution. 


Let x be the speed of the current.


The time equation is

    3%2F%285%2Bx%29 = 1.5%2F%285-x%29.


To solve, cross multiply and then simplify

    3*(5-x) = 1.5*(5+x),

    15 - 3x = 7.5 + 1.5x,

    15 - 7.5 = 3x + 1.5x,

       7.5   =    4.5x

         x   =  7.5/4.5 = 5/3.


ANSWER.  The speed of the current is  5/3 miles per hour.

Solved correctly.