1. Use proportions to solve problems.
equivalent ratios
proportion
cross products
constant of proportionality
Lesson 3 MI/Vocab

2. Interactive Lab: Solving Problems
Lesson 3 Key Concept 1

3. Write and Solve a Proportion
CLOTHING Melvin can decorate 8 t-shirts in 3 hours. At this rate, write and solve a proportion to find the time it will take him to decorate 20 t-shirts.
Write a proportion. Let t represent the time in hours.
shirts
shirts
time
time
Lesson 3 Ex1

4. Write and Solve a Proportion
Write the proportion.
Find the cross products.
Multiply.
Divide each side by 8.
Simplify.
Answer: It will take Melvin 7.5 hours to decorate 20 t-shirts.
Lesson 3 Ex1

5. CLOTHING Adrian can decorate 5 t-shirts in 2 hours
CLOTHING Adrian can decorate 5 t-shirts in 2 hours. At this rate, write and solve a proportion to find the time it will take her to decorate 18 t-shirts.
A. 6.5 hours
B. 7 hours
C. 7.2 hours
D. 7.6 hours A B C D
Lesson 3 CYP1

6. COOKING A recipe serves 10 people and calls for 3 cups of flour
COOKING A recipe serves 10 people and calls for 3 cups of flour. If you want to make the recipe for 15 people, how many cups of flour should you use?
Write a proportion. Let c represent the number of cups of flour needed to serve 15 people.
cups of flour
cups of flour
total people served
total people served
Lesson 3 Ex2

7. Find the cross products.
Multiply.
Divide each side by 10.
Simplify.
Answer: You will need 4.5 cups of flour to make the recipe for 15 people.
Lesson 3 Ex2

8. COOKING A recipe serves 12 people and calls for 5 cups of sugar
COOKING A recipe serves 12 people and calls for 5 cups of sugar. If you want to make the recipe for 18 people, how many cups of sugar should you use?
A. 6.5 cups
B. 6.7 cups
C. 7.2 cups
D. 7.5 cups A B C D
Lesson 3 CYP2

9. Write and Use an Equation
FOOD Haley bought 4 pounds of tomatoes for $ Write an equation relating the cost to the number of pounds of tomatoes. How much would Haley pay for 6 pounds at this same rate? for 10 pounds?
Find the constant of proportionality between cost and pounds.
The cost is $2.99 per pound.
Lesson 3 Ex3

10. Write and Use an Equation
Words
The cost is $2.99 times the number of pounds.
Let c represent the cost. Let p represent the number of pounds.
Variable
Equation
c = 2.99 ● p
Use this same equation to find the cost for 6 and 10 pounds of tomatoes sold at the same rate.
Lesson 3 Ex3

11. Replace p with the number of pounds.
Write and Use an Equation
Write the equation.
Replace p with the number of pounds.
Multiply.
Answer: The cost for 6 pounds of tomatoes is $17.94 and for 10 pounds is $29.90.
Lesson 3 Ex3

12. FOOD Cameron bought 3 pounds of apples for $11. 37
FOOD Cameron bought 3 pounds of apples for $ Write an equation relating the cost to the number of pounds of apples. How much would Cameron pay for 5 pounds at this same rate?
A. $18.95
B. $19.20
C. $19.85
D. $20.15 A B C D
Lesson 3 CYP3

13. TEETH: For every 6 people who say they floss daily, there are 14 people who say they do not. Write and Solve a proportion to determine out of 50 people how many you would expect to say they do floss daily.

14. ILLNESS: For every person who actually has the flu, there are 5 people who have the same symptoms but with only a cold. If a doctor sees 60 patients, write and solve a proportion to determine how many of these you would expect to only have a cold.

15. At this rate, how long will it take to print 10 photos?
PHOTOGRAPHY: It takes 3 minutes to print out 4 digital photos. Write an equation relating the number of photos, n, to the number of minutes, m.
At this rate, how long will it take to print 10 photos?