Given:
In 1950, the average car got 15 mpg.
In 2010, the average car got 23.5 mpg.
The objective is to find the percentage change in gas mileage.
The formula to find the percentage change is,
![\text{Percentage change=}\frac{Final\text{ value-Initial value}}{Final\text{ value}}*100](https://img.qammunity.org/2023/formulas/mathematics/high-school/pdtve7g4sfu3sq77ptk88wqjco4gylf4t5.png)
Now, substitute the given values in the above formula.
![\begin{gathered} Percentage\text{ change=}(23.5-15)/(15)*100 \\ =56.67\text{ percentage.} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/jzsxd0tmy86dvoqayadfvrnkaset5rah33.png)
Hence, the percecntage change in gas mileage is 56.67%.