#### Answer

The percent change in the price of a gallon of gasoline is 140%.
It is a percent increase.

#### Work Step by Step

To find the percent change, we use the following formula:
percent change = $\frac{New\ amount\ -\ Original\ amount}{Original\ amount}$ $\times$ 100%
The original price was 2.50 dollars a gallon. The new price became 6.00 dollars. Substituting these values into the formula yields:
percent change = $\frac{6.00\ -\ 2.50}{2.50}$ $\times$ 100%
percent change = $\frac{3.50}{2.50}$ $\times$ 100%
percent change = 1.4 $\times$ 100%
percent change = 140%
Because the percent change is a positive number, it is a percent increase.