Transcript Chapter 6 Lesson 8 Percent of Change pgs. 304-308

Chapter 6 Lesson 8
Percent of Change
pgs. 304-308
What you will learn:
Find percent of increase
Find percent of decrease
Vocabulary:
• Percent of change (304): tells the percent an
amount has increased or decreased in
relation to the original amount
• Percent of increase (305): when an amount
increases
• Percent of decrease (306): when the amount
decreases, the percent of change is negative
Suppose the length of rectangle A is
increased from 4 units to 5 units.
4 units
-----------------------> 5 units
Rectangle A had an initial area of 8 square
units. It increased to 10 square units. This is
a change in area of 2 square units. The
following ratio shows this relationship.
change in area =2 = 1 or 25%
original area 8 4
That means, compared to the original area, the new area
increased by 25%
Example1: Find Percent of Change
Find the percent of change from 25 cm to 36 cm
Step 1: Subtract to find the amount of change
36 - 25 = 11 new measurement - old measurement
Step 2: Write a ratio that compares the amount of
change to the original measurement. Express the
ratio as a percent
percent of change = amount of change
original measurement
= 11
25
= .44 = 44%
The percent of change from
25 cm to 36 cm is 44%
Example 2: Find Percent of Increase
In 2000, there were 356 endangered species in
the U.S. One year later, 367 species were
considered endangered. What was the
percent of change?
Step 1: Subtract to find the amount of change.
367 - 356 = 11 new amount - original amount
Step 2: Write a ratio that compares the amount of change
to the original amount. Express the ratio as a percent.
Percent of change = amount of change
original amount
11 = .0308988764
Write the decimal as a %
356
= 3.1%
Example 3: Multiple Test Item
Refer to your book pg 305.
Example 4: Find Percent of Decrease
Seattle, Washington, receives an average of 6.0 inches of
Precipitation in December. In March, the average
precipitation is 3.8 inches. What is the percent of change in
Precipitation from December to March?
Step 1: Subtract to find the amount of change.
3.8 - 6.0 = -2.2 (ending precipitation - beginning precipitation)
Compare the amount of change to the beginning precipitation
percent of change = amount of change
beginning precip.
-2.2 = -0.36666 <----change to a percent
6
-36.7% This is a percent of decrease
Your Turn!
Find the percent of change. Round to the nearest tenth
if necessary and state whether the percent of change is
a percent of increase or a percent of decrease.
A. From 68 min to 51 min
51-68 = -17
-17 = -.25 = -25% Decrease
68
B. From 257m to 243m
243-257= -14
-14 = -.0544= -5.4% Decrease
C. From $289 to $762
257
762-289=473
473 = 1.6366 = 163.7% Increase
289
D. Suppose 36 videos are added to a video collection
that has 24 videos. What is the percent of change?
60-24=36
36 = 1.5 =150% Increase
24