Bell work

Solve each proportion:1. 5 = x

6 122. a = 2

18 43. 2 = 5

6 t

10

9

15

Proportions Day 2

Ratio and Proportion

x28

54

=

Let x be the number of potatoes required to serve 28 people.

Cross Products 4x = 5 (28)4x = 140

A recipe that serves 4 people uses 5 potatoes. How many potatoes are needed to serve 28 people?

Since the recipe is the same, we have two equivalent ratios:

# of people:# of potatoes:

# 1

# 2

# 3

# 4 Divide by 4 to find x 4

1404x4

=

x=35 potatoes

Easy way to remember

100

%

of

is

is = part of the whole (sometimes called part of base)

of = total (sometimes called the base)

% always goes over 100 since 100% = one whole

𝑝𝑎𝑟𝑡h𝑤 𝑜𝑙𝑒

=¿

Types of Percent Problems

Type Example Proportion

Find the % 3 is what percent of 4?

3 = P 4 100

Find the part What number is 75% of 4?

is = 75 4 100

Find the base 3 is 75% of what number

3 = 75 of 100

Finding a Part of a BaseYour class has raised 80% of its goal of $8000 for a trip to Washington, D.C. How much money has your class raised for the trip?

= 6400

Substitute 80 for p and 8000 for of.

Solve using mental math or cross products

ANSWER Your class has raised $6400 for the trip to Washington, D.C.

100

80

8000

is

100

%

of

is Write percent equation.

Finding a PercentA service club is planting seedlings as part of a project. Out of 250 newly planted seedlings, 15 did not bloom. What percent of the seedlings did not bloom?

Write a percent proportion.

Substitute 15 for is and 250 for of.

6%ANSWER

6% of the seedlings did not bloom.

100

%

of

is

100

%

250

15

Solve using cross products

Finding a Base

Marc received 273, or 35%, of the votes in the student council election. How many students voted in the election?

Student Council

Write percent equation.

Substitute 273 for is and 35 for %.

780 = of

780 students voted in the election.ANSWER

100

%

of

is

100

35273

of

Solve using cross products

Find the Percent

72 is what percent of 160?

Find the cross products: 72100 = 160P Simplify: 7200=160P

Divide: 7200 = 160P 160 160

Solve: 45 = P

So 72 is 45% of 160

100

%

of

is

100

%

160

72

Find the Base

• 27 is 90% of what number?

Cross Products: 27100 = b90 Simplify: 2700 = 90b

Divide: 2700 = 90b 90 90

Solve: 30= b So, 27 is 90% of 30

100

%

of

is100

9027

of

Apply the Percent Proportion

• If 12 of the 75 animals in a pet store are parakeets, what percent are parakeets?

Cross Products: 12100 = 75PSimplify: 1200 = 75P Divide: 1200 = 75P

75 75Solve: 16 = P So, 16% of the animals are

Parakeets

100

%

of

is100

%

75

12

Apply the Percent Proportion

• Of the fish in an aquarium, 26% are angelfish. If the aquarium contains 50 fish, how many are angelfish?

a100 = 5026 100a = 1300

a = 13So, 13 fish are angelfish

100

%

of

is

100

26

50

is

Your Turn! Use the percent proportion to solve each problem.

17 is what percent of 85?

36 is 72% of what number?

What is 84% of 150?

17 = P 85 100 P = 20 20%36 = 72

b 100 b = 50

a = 84 150 100 a = 126

Practice: