SOLUTION: the river current is 8 mph. a jet ski can travel 34 miles downstream in the same time that it takes to go 18 miles upstream. what is the speed of th jet ski with no current?

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Question 996929: the river current is 8 mph. a jet ski can travel 34 miles downstream in the same time that it takes to go 18 miles upstream. what is the speed of th jet ski with no current?
Answer by josgarithmetic(39614) About Me  (Show Source):
You can put this solution on YOUR website!
Basic rule is RT=D. 

WhichWay  speed   time     distance
DOWN      r+8      t         34
UP        r-8      t         18


You could assign variables to everything; but for your particular example, highlight_green%2834%2F%28r%2B8%29=18%2F%28r-8%29%29.



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Some discussion of the solution:

Making a data table often helps to see what is happening with the numbers.

The variable, t, is for the same amount of time in both directions. The basic uniform travel rates relationship gives
system%28%28r%2B8%29t=34%2C%28r-8%29t=18%29;

and the unknown t can be solved for both of those equations in terms of the unknown r:
system%28t=34%2F%28r%2B8%29%2Ct=18%2F%28r-8%29%29 and since you know that these two expressions for t must be equal, you can say the equation 34%2F%28r%2B8%29=18%2F%28r-8%29 and solve this for r, the number being asked for in the question.