Proportions

Wednesday, November 24Math Workshop 3rd Period

1. What is the sum of 3 ½ and 2 ½ ?

A. 5 2/4

B. 6

C. 12/2

D. 7

2. If Kayla had 7 2/9 cups of sugar and she used 3 1/3 on a

pumpkin pie, how much sugar does she have left?

A. 3.88

B. 4 1/6

C. 3 8/9

D. 35/9

3. What is the √81?

A. 10

B. 9

C. 8

D. 9.1

4. What is 122?

A. 121

B. 144

C. 3.46

D. 1728

5. What is ¾ ÷ 5?

A. 1/5

B. .15

C. 3/20

D. 4 ¼

6. For every 5 bowl in your kitchen, you have 11 spoons. If you have 15 bowls, how

many spoons would you have?

Remember – set this up as a proportion!

A. 22 bowls

B. 20 bowls

C. 27 bowls

D. 33 bowls

REVIEW: Proportions

In order to solve problems involving proportions, you should be able to:

 • work with fractions • set up ratios• set up equivalent fractions • cross multiply • solve one-step equations

A proportion sets two ratios equal to each other. In one ratio, one of the quantities is not known. You then use cross multiplication and solve the equation for the missing value. For example:

3 = x 5 10

Suppose it takes 48 chicken fingers to feed Mr. Young’s 4th grade class of 20 students. How many chicken fingers would be needed for 30 students? There are several ways to approach this problem. Most students feel that the easiest way is to set up a ratio with the first piece of information given in the problem. In this problem, the ratio would be chicken fingers students

According to the problem, it takes 48 chicken fingers for 20 students which can be expressed as the ratio 48

20

Now we need to set up the second ratio for the larger group of students keeping in mind that the number of chicken fingers goes in the numerator and the number of students goes in the denominator. We do not know the number of students, so we can call it x. The number of students is 30. This gives the ratio x 30

Solving a proportion means that we are now going to set the two ratios equal to each other and solve. 

1. 48 = X

20 30

2. 48 x 30 = 20 x X

3. 1440 = 20X

4. 72 = X

Videos

http://www.teachertube.com/viewVideo.php?video_id=21931&title=Solving_a_Proportion_Problem

http://www1.teachertube.com/viewVideo.php?video_id=2934

Class Work

David read 40 pages of a book in 50 minutes. How many pages should he be able to read in 80 minutes?

40 Pages = X

50 Minutes 80 Minutes

Class Work

Tyshawn takes inventory of his closet and discovers that he has 8 shirts for every 5 pairs of jeans. If he has 40 shirts, how many pairs of jeans does he have?

8 Shirts = 40 Shirts

5 Jeans X

Class Work

If 4 grapefruits sell for 79 cents, how much will 6 grapefruits cost?

4 Grapefruit = 6 Grapefruit

79 Cents X

Class Work

Kim found out that after working 9 months she had earned 6 days of vacation time. How many days will she have earned after working two years? (Hint: There are 12 months in one year.)

9 Months = 24 Months

6 Vacation Days X

Determine Whether the Ratios Form a Proportion

3 = 42

4 49

2 = 12

3 18

4 = 20

6 30

Review Homework

Problems 1 thru 22 Students will come to the board and solve the

problems. Students should fill in their homework with

the correct answers (or any answers if they did not finish their homework).

Class Work

1. If you can buy one can of pineapple chunks for $2 then how many can you buy with $10?

1 (pineapple) = X (pineapple)

$2 $10

Class Work

One jar of crushed ginger costs $2. How many jars can you buy for $4?

1 (ginger) = X (ginger)

$2 $10