SOLUTION: On Monday Roger drove to work in 45 minutes. On Tuesday he averaged 12 miles per hour more, and it took him 9 minutes less to get to work. How far does he travel to work?

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Question 1742: On Monday Roger drove to work in 45 minutes. On Tuesday he averaged 12 miles per hour more, and it took him 9 minutes less to get to work. How far does he travel to work?
Answer by longjonsilver(2297) About Me  (Show Source):
You can put this solution on YOUR website!
let the speed on Monday be x mph. It takes him 45 minutes (which is 3/4 of an hour), so using speed=distance/time gives:
x=%28d%2F%283%2F4%29%29 or x=%284d%29%2F3. This is equation 1.
On Tuesday, speed is 12mph more, so it is x+12. His time is 9 minutes less, meaning 36 minutes, which is 3/5 of an hour. REMEMBER, the speed is miles per HOUR, so all distances must be miles and all times must be HOURS.
so, its equation is %28x%2B12%29=%28%285d%29%2F3%29. This is equation 2.
Equation 1 re-arranges to be 3x=4d
Equation 2 re-arranges to be %283x%2B36%29=5d.
We can substitute equation 1 into equation 2 and we get d=36miles.
cheers
Jon.