1. Splash Screen

2. Solve proportions. proportional proportion cross product
Main Idea/Vocabulary

3. KC 1

4. Identify Proportional Relationships
MATH Before dinner, Mohammed solved 8 math problems in 12 minutes. After dinner, he solved 2 problems in 3 minutes. Is the number of problems he solved proportional to the time?
Method 1 Compare unit rates (We did this before).
Since the unit rates are equal, the number of math equations is proportional to the time in minutes.
Example 1

5. KC 1

6. Identify Proportional Relationships
Method 2 Compare ratios by comparing cross products. ?
8 × 3 = 12 × 2 Find the cross products. ?
24 = 24 Multiply. 
Answer: Since the cross products are equal, the number of math equations is proportional to the time in minutes.
Example 1

7. Determine if the quantities $30 for 12 gallons of gasoline and $10 for 4 gallons of gasoline are proportional.
A. yes
B. no A B
Example 1

8. 5x = 8 ● 18 Find the cross products. 5x = 144 Multiply.
Solve a Proportion
Write the proportion.
5x = 8 ● 18 Find the cross products.
5x = 144 Multiply.
Divide each side by 5.
x = 28.8
Answer: x = 28.8
Example 2

9. A. k = 9.4
B. k = 12
C. k = 10.8
D. k = 18.6 A B C D
Example 2

10. 3.5 ● n = 14 ● 6 Find the cross products. 3.5n = 84 Multiply.
Solve a Proportion
Write the proportion.
3.5 ● n = 14 ● 6 Find the cross products.
3.5n = 84 Multiply.
Divide each side by 3.5.
n = 24 Simplify.
Answer: The solution is 24.
Example 3

11. A. w = 5.25
B. w = 5.5
C. w = 5.75
D. w = 6.25 A B C D
Example 3

12. length Write a proportion. width
FLAGS According to specifications, the ratio of the length of the U.S. flag to its width must be 1.9 to 1. How long must a U.S. flag be if it is designed to have a width of 2.5 feet?
length Write a proportion. width
Find the cross products.
Multiply.
Answer: The length of a U.S. flag having a width of 2.5 feet must be 4.75 feet.
Example 4

13. SCHOOL The ratio of boys to girls at Blue Hills Middle School is 4 to 5. How many girls attend the school if there are 96 boys?
A. 72 girls
B. 108 girls
C. 120 girls
D. 148 girls A B C D
Example 4

14. End of the Lesson
End of the Lesson