1. Warm Up
Problem of the Day
Lesson Presentation
Lesson Quizzes

2. Use the table to write each ratio.
Warm Up
Use the table to write each ratio.
1. giraffes to monkeys
2. polar bears to all bears
3. monkeys to all animals
4. all animals to all bears 4
Polar Bears 17
Monkeys 2
Giraffes 3
Brown bears
2:17
4:7
17:26
26:7

3. Problem of the Day
A carpenter can build one doghouse in one day. How many doghouses can 12 carpenters build in 20 days?
240

4. Learn to write and solve proportions.

5. Vocabulary
proportion

6. A proportion is an equation that shows two equivalent ratios.2 1 __ 4 = 4 2 __ 8 = 2 1 __ 6 3 =
Reading Math 2 1 __ 4 2 __
Read the proportion = as “two is to
one as four is to two.”

7. Additional Example 1: Modeling Proportions
Write a proportion for the model.
First write the ratio of hearts to stars.
number of hearts
number of stars 4 8 __ =
Next separate the hearts and stars into two equal groups.

8. Additional Example 1 Continued
Now write the ratio of hearts to stars in each group.
number of hearts
number of stars 2 4 __ = 4 8 __ 2 4 __
A proportion shown by the model is = .

9. Check It Out: Example 1
Write a proportion for the model.
First write the ratio of faces to moons.
number of faces
number of moons 2 6 __ =
Next separate the faces and moons into two equal groups.

10. Check It Out: Example 1 Continued
Now write the ratio of faces to moons in each group.
number of faces
number of moons 1 3 __ = 2 6 __ 1 3 __
A proportion shown by the model is = .

11. Cross products in proportions are equal4 8 __ 2 = 3 5 __ 9 15
___ = 9 6 __ 3 2 = 14 7 __ 2 1 =
8 • 2 =
4 • 4
5 • 9 =
3 • 15
6 • 3 =
9 • 2
7 • 2 =
14 • 1
16 = 16
45 = 45
18 = 18
14 = 14
Ttoto solo

12. Find the missing value in the proportion.5 6 __ n 18 =
Find the cross products.
6 • n =
5 • 18
The cross products are equal.
6n = 90
n is multiplied by 6. 6n 6
___ 90 6
___ =
Divide both sides by 6 to undo the multiplication.
n = 15

13. Find the missing value in the proportion.3 5 __ n 15 =
Find the cross products.
5 • n =
3 • 15
The cross products are equal.
5n = 45
n is multiplied by 5. 5n 5
___ 45 5
___ =
Divide both sides by 5 to undo the multiplication.
n = 9

15. In a proportion, the units must be in the same order in both ratios.
Caution!
In a proportion, the units must be in the same order in both ratios.
tbsp
gal
___
tbsp
gal
___ =
gal
tbsp
___
gal
tbsp
___ or =

16. A glacier moves about 3 inches every 9 hours
A glacier moves about 3 inches every 9 hours . At that rate, about how far does the glacier move in 36 hours?

17. Jackson bikes 2 miles in 15 minutes
Jackson bikes 2 miles in 15 minutes. At that rate, how many miles will he bike in 45 min? .

18. Lesson Quizzes
Standard Lesson Quiz
Lesson Quiz for Student Response Systems

19. 1. Write a proportion for the model.
Lesson Quiz
1. Write a proportion for the model.
Find the missing value in each proportion.
= =
4. The label on a bottle of salad dressing states that there are 3 grams of fat per tablespoon. If you use 3 tablespoons, how many grams of fat would you be getting? 2 6 __ 1 3 __ = 9 5 __ 45 x __ p 36 __ 5 6 __
x = 25
p = 30
9 g

20. Lesson Quiz for Student Response Systems
1. Identify a proportion for the model.
A B.
C D.

21. Lesson Quiz for Student Response Systems
2. Identify the missing value in the proportion.
A. x = B. x = 56
C. x = D. x = 49

22. Lesson Quiz for Student Response Systems
3. Identify the missing value in the proportion.
A. n = 6 B. n = 51
C. n = D. n = 102

23. Lesson Quiz for Student Response Systems
4. According to the label, 1 tablespoon of mixed fruit concentrate should be used to prepare 200 ml of juice. How many tablespoons of concentrate would you use to prepare 800 ml of juice?
A. 2 tbsp B. 3 tbsp
C. 4 tbsp D. 5 tbsp