Algebra 1 Common Core Student Edition, Grade 8-9

Change Expressed

as a Percent

Common Core State Standards

N -Q .A .3 Choose a level o f accuracy appropriate to

limitations on measurement when reporting quantities.

MP 1, MP 2, MP 3, MP 4, MP 6

Objectives To find p ercen t change

To find th e relative error in linear a n d n o n lin ear m easu rem en ts

You have to

understand

percents to shop

fo r a good deal.

MATHEMATICAL

PRACTICES

m

Lesso n '

Vocabulary

• percent change


• percent increase


• percent decrease


• relative error


• percent erro r

In th e Solve It, th e 15% discount is a p ercen t change in th e price of th e sweater. A

percent change expresses an a m o u n t of change as a p ercen t of an original am ount. In

this lesson, you will learn how to calculate a percent change.

Essent ial Und er st and ing You can find a p ercen t change w h en you know the

original am o u n t a n d how m uch it has changed.

If a new a m o u n t is greater th a n th e original am ount, th e p ercen t change is called a

percent increase. If th e new a m o u n t is less th a n th e original am ount, th e p ercen t

change is called a percent decrease.

Key Concept Percent Change

P ercent change is the ratio of the a m o u n t of change to th e original am ount.

percent change, p% = ‘am ount of increase or decrease

original am ount

a m o u n t of increase = new a m o u n t - original a m o u n t

a m o u n t of decrease = original a m o u n t - new am o u n t

144 Chapter 2 So l v i n g Eq u a t i o n s