1. Ratio, Proportion and Similarity
Objectives:
To write ratios.
To solve proportions.
To use proportions to find the measure of a side of a similar figure.

2. Ratios A ratio is a comparison of two numbers by division
We can compare the ratio of wins to losses for the Texas Rangers in three ways:
to 25
2. 19: 25 3.
Team W L
California 22 26
Seattle 20 25
Texas 19
Oakland 13 33

3. Examples Team W L California 22 26 Seattle 20 25 Texas 19 Oakland 1333
Examples
1. Write the win-loss ratio for California as a fraction in simplest form.
2. Write the ratio for games won by Seattle to total games played.

4. Guided Practice: Write each ratio as a fraction in simplest form
6 absences in 180 school days
300 students to 20 teachers
76 heartbeats per 60 seconds
300 miles to 15 gallons

5. Proportions
A proportion is a statement that two ratios are equivalent or equal. If two ratios are equivalent we say that they are proportional
Determine if the ratios 9 to 12 and 18 to 24 are proportional.

6. Examples: Determine if the ratios are proportional
20:8 and 16:4
15 to 45 and 7 to 28

7. Guided Practice: Determine if the ratios are proportional
3 to 6, 4 to 8
12 to 18, 20 to 24
9 to 3, 6 to 2
20:16, 35:28 5.

8. Solving proportions
To solve a proportions, cross multiply then solve the equation
Solve

9. Examples

10. Hw: p.281/7-24, p. 285/7-18, 24-26, Worksheet