Final answer:
The percent change in the cost of a gallon of milk from 2000 to 2015 is 42.7% after rounding to the nearest tenth.
Step-by-step explanation:
To determine the percentage change in the cost of a gallon of milk from the year 2000 to 2015, we use the formula:
Percent Change = (New Price - Old Price) / Old Price × 100%
Using the given prices, the calculation is as follows:
Percent Change = ($3.98 - $2.79) / $2.79 × 100%
Percent Change = $1.19 / $2.79 × 100%
Percent Change = 0.4265 × 100%
Percent Change = 42.65%
After rounding to the nearest tenth, the percent change is 42.7%.