1. Chapter 7: Similarity

2. 7-1 Ratios and Proportions
Objective
To write ratios and solve proportions

3. Write the ratio in simplest form.
A comparison of two numbers
Notation: words, colon, fraction or decimal (b 0)
Proportion:
An equation stating two ratios are equal
Example:
Write the ratio in simplest form.

4. Solving a Proportion Steps: 1. Cross multiply 2. Divide
Solve the following proportions:

5. Additional Examples 6120 = 24(x + 50) 714 = 21(x – 23)

6. Example 1
In a photograph, Dan is 2.5 inches tall and his sister Emma is 1.5 inches tall. Dan’s actual height is 70 inches.
What is Emma’s actual height?
Dan’s picture height
Dan’s actual height
2.5 70 =
1.5 x
Emma’s picture height
Emma’s actual height
2.5x = 105
x = 42 inches

7. Extremes and Means
The first and last numbers in a proportion are the extremes.
The middle two numbers in a proportion are the means.

8. Properties of Proportions

9. Write an equivalent proportion.
7-1 p. 436: odd