Question

The average price of gasoline in 1955 was $0.23 a gallon. In 2004 the average price of gas was $1.75 a gallon. How do you find the average rate of change of the price of gas per gallon in dollars per year?

Answer 1

The average rate of change is `$0.03` per gallon per year.

Explanation:

Let's create two coordinates/points with the given information. Typically, the time/year is on the `x` axis, so those are the `x`-coordinates.
`(1955, 0.23)` and `(2004, 1.75)`

To find the slope given two points, we use the formula `"rise"/"run"`, or `(y_2-y_1)/(x_2-x_1)`.

Plug in the given points into the formula:
`(1.75-0.23)/(2004-1955) = 1.52/49 ~~ 0.03`