1. 3.9 Proportions Goal to solve problems involving proportions

2. RatioProportion Ratio and Proportion A ratio of two quantities is a comparison, often expressed as a fraction. An equation that states that two ratios are equal is called a proportion.

3. To Solve Proportions… Cross multiply and set their products = to each other Ex: a = b c d so ad = cb

4. y = 20 Example:

7. Proportions In Word Problems Comparing units Same units go in the numerator Same units go in the denominator

8. Strategies With Word Problems Read the problem at least two times Write down the information you have Identify what you are trying to find Draw a picture Set up an equation Solve Check

9. The property tax on a house is $8 per $1000 of assessed value. What is the tax on a house assessed at $165,000? 8 165,000 =1000t

10. On a road map 3 inches represents 40 miles. If two cities are 10 inches apart on the map, how many miles is it from one to the other?

11. Assignment Page 150 (10-24 even and 25-38 all )