Fred drives an average of $15,000$ miles per year, and his car gets $20$ miles per gallon of gasoline.

  • The average cost of gasoline is $\$3.25 $ per gallon.
  • He buys a new car. In his new car Fred continues to average $15,000$ miles per year, and the average cost of gasoline remains the same.

Approximately how many more miles per gallon does the new car get of Fred has a savings of $\$650$ per year on gasoline?

So for this this is what I've got: $15000/20=750$ to find the gallons drove and than multiply that by $3.25$ so I would get $750\cdot 3.25=2437.5$ and I subtract that by $650$ because $650$ is saved.

Now I have stuck. after this what do i do?

And sorry for not editing this correctly, I'm using my phone.

  • $\begingroup$ You know that he paid $2437.5-650=1787.5$ dollars and each gallon costs $3.25\$ $. How much gallons he paid for? In total he drove for 15000 miles. How much miles he drove for each gallon? $\endgroup$ – Galc127 Jun 1 '16 at 17:41

Let $M$ be the number of miles driven, $m$ be the mileage in miles per gallon, and $P$ be the price per gallon in dollars.


$$\left[\frac{M_{old}}{m_{old}} - \frac{M_{new}}{m_{new}}\right]P = 650.$$

The only unknown here is $m_{new}$ so you can solve for it.


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