Page 90 - Math Course 3 (Book 1)

Rates of Change

Compare Rates of Change Negative Rate of Change

Example Example

INCOME COOKIES
The table shows the yearly incomes of two Natalie sold 100 cookies in 5 hours. The graph
families. Compare the rates of change. shows the relationship between the hours spent
selling and the number of cookies that remained.
Find the rate of change.
Income($)
Years
Miller Jonesses 140
120
2001 49,000 50,000

2002 51,000 52,000 100
80
2003 52,000 54,500 Cookies 60

2004 55,000 57,000 40

change in y 20
Millers rate of change = change in x

55,000 – 49,000 1 2 3 4 5 6
=
2004 – 2001 Hours
or 2000
Rate of change = number of cookies remaining
change in y hours spent selling cookies
Jonesses rate of change =
change in x 0 – 100
=
57,000 – 50,000 5 – 0
= 2004 – 2001 – 100
=
or 2333.33 5
= –20

58 Answer The rate of change is –20 cookies
per hour or a decrease of 20
Dollars(Thousand) 54 Your Turn!
56
cookies for each hour selling.

52

50

48 Real World Example
SUMMER CAMP
0 The graph shows the number of campers enrolled
2001 2002 2003 2004 at a summer camp during its first five years of

Year operation. Find the rate of change from Year 2 to
Year 5.

The income of the Joneses
increases at a faster rate than the
income of the Millers. A steeper
Answer
line on the graph indicates a
greater rate of change for the
Joneses.

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