7th Grade Math

Chapter Study Guide and Review

368 Percent

Proportions and Equations (continued)

The Percent Equation (Lesson 2C)

Write an equation for each problem.

Then solve. Round to the nearest tenth

if necessary.

26. 32 is what percent of 50?


27. 65% of what number is 39?


28. SALONS A salon increased the sales of
    hair products by about 12.5% this week.
    If they sold 43 hair products last week,
    how many did they sell this week?

EXAMPLE 5 27 is what percent of 90?

27 is the part and 90 is the base. Let n

represent the percent.

part = percent · base

27 = n · 90 Write an equation.

_^27

90

= _^90 n

90

Divide each side by 90.

0.3 = n The percent is 30%.

So, 27 is 30% of 90.

PSI: Determine Reasonable Answers (Lesson 2D)

Determine a reasonable answer for the

problem.

29. CABLE TV In a survey of 1,813 consumers,
    18% said that they would be willing to
    pay more for cable if they got more
    channels. Is 3.3, 33, or 333 a reasonable
    estimate for the number of consumers
    willing to pay more for cable?

EXAMPLE 6 Out of 394 students, 24.8%

participate in music programs. What is a

reasonable estimate for the number of

students who participate in music

programs?

394 × 0.248 400 × 0.25 or 100 students

So, about 100 students.

Lesson 2

Applying Percents

Percent of Change (Lesson 3B)

Find each percent of change. Round to

the nearest whole percent if necessary.

State whether the percent of change is

an increase or decrease.

30. original: 172 31. original: $200
    new: 254 new: $386


31. original: 75 33. original: $49.95
    new: 60 new: $54.95


32. COMICS Tyree bought a collectible comic
    book for $49.62 last year. This year, he sold
    it for $52.10. Find the percent of change of
    the price of the comic book. Round to the
    nearest percent.

EXAMPLE 7 A magazine that originally

cost $2.75 is now $3.55. Find the percent of

change. Round to the nearest whole

percent.

Find the amount of change.

3.55 - 2.75 = 0.80

percent of change =

amount of change

__

original amount

= _0.802.75 Substitution

≈ 0.29 Simplify.

The percent of change is about 29%. Since the

percent of change is positive, this is a percent

of increase.

Lesson 3

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