Mileage

I took a fairly long trip and I thought that made for a good and not extremely difficult application problem. It is a two-parter, with a little algebra, but not to hard.

I drove roughly 600 miles. I was on a freeway the entire time, so was getting a healthy 39 miles per gallon. The price of gas seemed was about $3.60 per gallon. How much did my trip cost me?

How much it cost me depends on how many gallons I used. So, how many gallons did I use? Since miles per gallon = miles/gallons, we have 39 = 600/x. It turns out that x = 15.39 gallons.

Again we can use a fairly obvious equation: cost per gallon = cost/gallons. Since the cost for each gallon is $3.60, we have 3.60 = x/15.39. This gives us x = $55.40.