SOLUTION: I travel 45 miles by car. It runs out of gas. I walk 3 miles. It takes me a total of 90 minutes. I travel 15 times faster in a car than walking. What is my driving speed.

Question 454779: I travel 45 miles by car. It runs out of gas. I walk 3 miles. It takes me a total of 90 minutes. I travel 15 times faster in a car than walking. What is my driving speed.
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
There are 2 different rates, so you need 2 different equations:
Let = driving speed
Let = time spent driving
In car:

(1)
Walking:
(2) ( units in miles, hrs, and miles/hr )
There are 2 equations and 2 unknowns, so it's solvable
(2)
(2)
Substitute (1) into (2)
(2)
(2)
(2)
(2) mi/hr
check answer:
(1)
(1)
(1) hrs
and
(2)
(2)
(2)
OK
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