SOLUTION: two cars leave from the same point at the same time, traveling in opposite directions. one travels 15 mph slower than the other. after 6 hours, they are 639 miles apart. Find the r

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Question 835077: two cars leave from the same point at the same time, traveling in opposite directions. one travels 15 mph slower than the other. after 6 hours, they are 639 miles apart. Find the rate of each car.
Found 2 solutions by josgarithmetic, rfer:
Answer by josgarithmetic(39616) About Me  (Show Source):
You can put this solution on YOUR website!
_____________speed____________time_____distance_______
Faster_______r_________________6_______r*6____________
Slower______r-15_______________6_______(r-15)*6_______
Total__________________________________639

Last part of the description and the distance column give the equation,
highlight%28r%2A6%2B%28r-15%29%2A6=639%29
-
6r%2B6r-90=639
12r=639%2B90
12r=729
highlight%28r=61%29 mph


(Actual computation to r=60.75)

Answer by rfer(16322) About Me  (Show Source):
You can put this solution on YOUR website!
6(x-15+x)=639
6x-90+6x=639
12x=639+90
12x=729
x=60.75
x-15=45.75