Pre-Algebra Chapter 6 - Ramsey School District

Practice and Apply
Homework Help
For
Exercises
See
Examples
10–18, 20, 21 1, 2, 4
19 3
Extra Practice
See page 739.
Find the percent of change. Round to the nearest tenth, if necessary. Then
state whether the percent of change is a percent of increase or a percent of
decrease.
10. from 25 cm to 36 cm 11. from $10 to $27
12. from 68 min to 51 min 13. from 50 lb to 44 lb
14. from $135 to $120 15. from 257 m to 243 m
16. from 365 ft to 421 ft 17. from $289 to $762
18. WEATHER 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?
19. POPULATION In 1990, the population of Alabama was 4,040,587.
In 2000, the population was 4,447,100. Find the percent of change from
1990 to 2000.
20. Suppose 36 videos are added to a video collection that has 24 videos.
What is the percent of change?
21. A biology class has 28 students. Four of the students transferred out
of the class to take chemistry. Find the percent of change in the number
of students in the biology class.
22. BUSINESS A restaurant manager wants to reduce spending on supplies
10% in January and an additional 15% in February. In January, the expenses
were $2875. How much should the expenses be at the end of February?
23. SCHOOL Jiliana is using a copy machine to increase the size of a 2-inch
by 3-inch picture of a spider. The enlarged picture needs to measure
3 inches by 4.5 inches.
www.pre-alg.com/self_check_quiz
What enlargement setting on the copy machine should she use?
24. CRITICAL THINKING Explain why a 10% increase followed by a
10% decrease is less than the original amount if the original amount
was positive.
25. WRITING IN MATH Answer the question that was posed at the beginning
of the lesson.
How can percents help to describe a change in area?
Include the following in your answer:
• an explanation describing how you can tell whether the percent of
increase will be greater than 100%, and
• an example of a model that shows an increase less than 100% and one
that shows an increase greater than 100%.
Lesson 6-8 Percent of Change 307