1. Ratios and Proportions
Cornell Notes #8

2. Comparison between two numbers.
Ratio
Real life
Comparison between two numbers.
Example: 5 kids went to the party. Only 2 kids spent the night.
Ratio is 2/5 (kids who spent the night/total kids at the party)
What is the ratio of boys to girls in this class.

3. Ratio How to write a ratio Is the ratio of girls to boys the same? NO.
When writing a ratio, ORDER matters.
What is the ratio of girls to boys?
2 , 2 to 3, 2:3 3

4. How many basketballs to footballs are there?
Ratio
How many basketballs to footballs are there?
What does that mean?
For every 5 basketballs there are 6 footballs.
The ratio is 5 to 6.

5. First quantity to Second quantity 5 : 6
What are some other ways we can write the ratio of basketball to footballs?
Every ratio can be written in 3 ways:
5 to 6
First quantity to Second quantity
5 : 6
First quantity : Second quantity 5 6
First quantity divided by the second quantity (as a fraction).

6. Write a ratio for each of the following:
There are 12 girls and 17 boys in English class. What is the ratio of boys to girls?
Basketball season: the team won 18 games and lost 12. What is the ratio of games lost to games won?
The pound had 12 cats and 17 dogs. What is the ratio of cats to dogs.

7. Proportion
16 = n
Has an equal sign
States that two ratios are equal.
Has two cross products that are equal to each other.
Used to find missing values.

8. Solve the proportion.
Set up proportion.
Cross multiply
Simplify multiplication
Divide
Solve
The ratio of boys to girls is 4 to 5. There are 12 boys in the class. How many girls are in the class?
4 boys = 12 boys
5 girls ? G
2. 4 X g = 5 X 12
3. 4g=60
4g = 60
5. g=60÷4 or g=15

9. Practice Tell if the ratios form a proportion: 6/14, 3/7 14/35, 8/20
6/14, 3/ /35, 8/20
Write ratios for the following:
There are 6 girls and 10 boys in the class. Write the ratio of boys to girls.
There are 12 footballs and 7 basketballs. Write the ratio of basketballs to footballs.
There are 5 Mars bars and 7 Snickers bars. Write the ratio of Snickers bars to Mars bars.

10. Practice Solve these proportions using the 5 steps. 2/3 = n/27