SOLUTION: during a long distance race a competitor traveled a total of 28 kilometers over 8 hours. 18 k were traveled on river one and 10 k on river two. on the first river the competitor tr

Algebra ->  Rational-functions -> SOLUTION: during a long distance race a competitor traveled a total of 28 kilometers over 8 hours. 18 k were traveled on river one and 10 k on river two. on the first river the competitor tr      Log On


   

Question 1117143: during a long distance race a competitor traveled a total of 28 kilometers over 8 hours. 18 k were traveled on river one and 10 k on river two. on the first river the competitor traveled an average of 4 k per hour greater than she traveled on the second river. what was the average speed of the competitor on the first river?
Found 2 solutions by ikleyn, josgarithmetic:
Answer by ikleyn(52903) About Me  (Show Source):
You can put this solution on YOUR website!
.
Let x be the rate on the first river.


Your "time" equation is


18%2Fx + 10%2F%28x-4%29 = 8   hours.


It is "time" equation, because each fraction in the left side represents the time traveled on corresponding river.


To solve it, multiply both sides by x*(x-4). You will get a quadratic equation.
Simplify it and solve it by any method you know/(you like).


The answer is x= 6 kilometers per hour.  (I solved it mentally).


Answer by josgarithmetic(39630) About Me  (Show Source):
You can put this solution on YOUR website!
                 SPEED       TIME         DISTANCE

River1            r          18/r           18

River2           r-4         10/(r-4)       10

Total                         8             28

18%2Fr%2B10%2F%28r-4%29=8------solve this for r.