1. Proportions #27

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

3. Example 1: Modeling Proportions Julio spent $10 to buy 4 books at a garage sale. How much would Julio pay for 8 books at the garage sale?

4. Example 2 Paul spent $15 on 3 CDs at a store where all CDs are the same price. How much would it cost for Paul to buy 9 CDs?

5. Example 3 Beth drove 120 miles in 2 hours. She continues driving at the same rate and does not stop. How far will she have driven in 6 hours?

6. Cross products in proportions are equal CROSS PRODUCTS 3 5 __ 9 15 ___ = 4 8 __ 2 4 = 9 6 3 2 = 14 7 __ 2 1 = 8 2 =4 5 9 =3 15 16 = 16 45 = 45 6 3 =9 2 18 = 18 7 2 =14 1 14 = 14 FYI

7. Example 4: Using Cross Products to Complete Proportions Find the missing value in the proportion. 5 6 __ n 18 __ =

8. Example 5: Using Cross Products to Complete Proportions Find the missing value in the proportion. 3 9 __ 4 n =

9. Example 6 Find the missing value in each proportion. 3 5 __ n 15 __ = 3 15

10. Example 7 Find the missing value in each proportion. 2 13 __ 6 n = 2 n = 6 13 2n = 78 n = 39

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

12. Example 8 According to the label, 1 tablespoon of plant fertilizer should be used per 6 gallons of water. How many tablespoons of fertilizer would you use for 4 gallons of water?

13. Example 9 To make a certain shade of pink paint, mix 8 gallons of white paint with 3 gallons of red paint. How many gallons of white paint would you mix with 15 gallons of red paint to make this shade of pink?