SOLUTION: Two cars traveled from Elmhurst to Oakville, a distance of 100 miles. One car traveled 10 mph faster than the other and arrived 5/6 of an hour sooner. Find the speed of the faster
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Question 1138064: Two cars traveled from Elmhurst to Oakville, a distance of 100 miles. One car traveled 10 mph faster than the other and arrived 5/6 of an hour sooner. Find the speed of the faster car. Found 2 solutions by ikleyn, josgarithmetic:Answer by ikleyn(53765) (Show Source):
Let x = the speed of the faster car, in mph
Then the speed of the slower car is (x-10) miles per hour.
From the condition, you have this "time" equation
- = of an hour
To solve it, multiply both sides by 6x*(x-1). You will get
600*x - 600*(x-10) = 5x*(x-10).
6000 = 5x^2 - 50x
5x^2 - 50x - 6000 = 0
x^2 - 10x - 1200 = 0
(x-40)*(x+30) = 0.
The roots are 40 and -30. Only positive root is meaningful.
ANSWER. The faster car speed is 40 mph.
CHECK. The faster car spends = hours.
The slower car spends = hours.
The difference is = = = of an hour. ! Correct !
Solved and completed.
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From my post learn on how to write, to solve and to use the "time" equation.
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