Percent of Change The percent that a value

Percent of Change The percent that a value increases or decreases

Vocabulary (Section 5. 7 in book) • A percent of change is: – a ratio that compares the change in a quantity to the original amount. • For a percent of change, the proportion used is:

Ex 1) The Mitchell family bought a house several years ago for $120, 000. This year, they sold it for $150, 000. Find the percent of increase in the price of the house. A percent of increase is a percent of change. Subtract the house values to find the amount of change. Use the starting price as the original amount. The price of the house increased by 25%.

Ex 2) Mercer Middle School had 240 students last year. This year, there are 192 students enrolled. Find the percent of change in the number of students. Is this a percent increase or a percent decrease? The percent of change is a percent of decrease. Subtract the number of students to find the amount of change. Use the earlier number of students as the original amount. The number of students decreased by 20%.

Ex 3) The average speed of the winning race cars in the Indy 500 are shown in the table. Find the percent of change in speed from 1955 to 2010. Round your answer to the nearest whole percent. Year Speed (mph) 1922 94 1955 128 2010 162 The percent of change is a percent of increase. Subtract the speeds between 1955 and 2010 to find the amount of change. Use the average speed from 1955 as the original amount. The average speed increased by approximately 27%.