Question

The price per gallon of gasoline changes often. Most drivers pay close attention to those changes. Find the percent change in price for each of these cases.

a) increase from $4.00 per gallon to $4.20
b) increase from $3.00 per gallon to $3.75
c) decrease from $3.75 per gallon to $3.00

Answer 1

a) The amount of change is .20 (20 cents) so we need to find what percent of $4.00 is .20...
4 * x = .20
x = .20/4 = .05

Multiply by 100 (move decimal 2 places to the right) to change decimal to percent.

.05 = 5% increase

b)The increase is .75. What percent of 3.00 is .75

3 * x = .75
x = .75/3
x = .25 x 100 = 25% increase

c) The amount of change is .75 but this time we are going from 3.75 to 3.00 so we find out what percent .75 is of 3.75.

3.75 * x = .75
x = .75/3.75
x = .20 x 100 = 20% decrease