1. Lesson 85 Warm Up
Pg. 441

2. Using Cross Products to Solve Proportions
Course 1 Lesson 85
Using Cross Products to Solve Proportions

3. Cross Products
One way to compare fractions is by determining whether two fractions have equal cross products. The cross products of two fractions are found by cross multiplication.
3 6
4 8
3 x 8 = x 6 = 24.
The cross products are 24, so the fractions are equal.
Equal fractions have equal cross products.

4. Example 1

5. Example 2
Note: If the cross products are the same then the ratios form a proportion.

6. Example 3

7. Example 4

8. Lesson 85 Homework
Pg. 443 Practice, #1-10