1. By, Mrs. Muller
Proportions

2. Key Vocabulary Ratio: A comparison of two quantities by division.
Proportion: an equation stating that two ratios are equal.
Cross Product: multiplying the numerator of each ratio by the denominator of the other ratio

3. Proportion Ratios that are equal form a proportion.
In order to identify if they are a proportion make sure that they are equal to each other, by making sure to get to the new numerator and the new denominator you multiply by the same number.
Arithmetic
Algebra
12 _ 3
a _ c, where b ≠ 0 and d ≠ 0
b d

4. Example
It works!

5. Non Example
It does
Not
Work!

6. Cross Product Another Way is to check the cross products.
If the cross products are equivalent, then it is a proportion.
Arithmetic
Algebra
4 _ 12 15
4x15=5x12
a _ c , where b≠0 and d≠0
b d
ad=bc

7. Example
Is it a proportion?
Yes!

8. Solving One
You enlarge a photo that is 5 in. wide and 7 in. long. The sides of the new photo are in proportion to the original. The new photo is 14 in. wide. Find the length of the new photo. ?
length
7 inches
7 inches
width
5 inches
14 inches ?
19.6 inches ?
7 inches
14 inches
5 inches
5 inches ?
5 inches
98 inches inches
5 inches
14 inches
5 inches