Reteaching 4-1

Name

Class

Date

Reteaching 4-1

Ratio and Proportion

OBJECTIVE: Solving proportions

MATERIALS: None

An equation that states that two ratios are equal is called a proportion. In a proportion, the cross products are equal.

Example Use cross products to find out if the proportion 72 5 10 is true. 40 2 5 10 7 40 2 ? 40 = 7 ? 10

Write cross products.

80 = 70

Simplify.

80 2 70

Proportion is not true since 80 does not equal 70.

Use cross products to write and solve equations involving proportions. Solve: 5 5 25 x 6 5 5 25 x 6 5x = 6 ? 25

Set cross products equal to each other.

5x = 150

Simplify.

5x 5 150 5 5

Use the Division Property of Equality.

x = 30

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The cross products are 5x and 6 ? 25 or 150.

Simplify.

Exercises Determine if the proportions are true. (Hint: the cross products should be equal.) 6 5 12 1. 10 20

2. 54 5 78

5 24 3. 33 22 16

5 2 4. x 10 5

9 5 n 5. 180 60

2 5 8 6. x 36

4 7. 62 5 x

30 5 n 8. 125 100

3 5 t 9. 18 6

Solve each proportion.

10. 5t 5 35

8

7 11. 28 8 5x

Lesson 4-1 Reteaching

9 5 18 12. n 2

Algebra 1 Chapter 4