1. Ratios and Unit Rates

2. Ratio – a comparison of two quantities by division
Ratios can be written in three ways:
1) as a fraction in simplest form
2) with the word “ to ”
3) with a colon “ : ”

3. Examples:
Four out of five dentists surveyed recommend sugarless gum for their patients who chew gum
to :5 5
9 people out of 20 like chocolate ice cream
to :20 20

4. In a class of thirty students, thirteen are boys
In a class of thirty students, thirteen are boys. Write a ratio for the number of boys to students in the class.
13/ to :30
Write a ratio for the number of boys to the number of girls.
13/ to :17

5. Out of 100 students, 40 said they had afterschool jobs
Out of 100 students, 40 said they had afterschool jobs. Write a ratio for the number of students who had jobs to the number who did not.
40/60 = 2/3
40 to 60 = 2 to :60 = 2:3

6. 24 questions correct on a 100-question test
6 freethrows made out of 10 attempts
6/10 = 3/ to : 5
24 questions correct on a 100-question test
24/100 = 6/ to : 25
5 cookies eaten out of 20 cookies
5/20 = ¼ to : 4

7. Unit Rate – a rate for “one” of something; a ratio with a denominator of 1.
If three bananas cost $1.89, how much does one banana cost?
$1.89/3 = .63/1 banana

8. Examples:
You need to buy soda for a party. The store sells packs for $ Find the unit rate for one 12-pack?
$7.80/3 = $2.60/1

9. You travel 300 miles in five hours. Find the unit rate per hour.
300/5 = 60 miles/1 hour
A girl can jump rope 200 times in 4 minutes. What is the unit rate per minute?
200 / 4 = 50 times/1 minute

10. Determine which is the better buy:
You need to buy pizzas for a class party. You
can buy 4 large pizzas for $10.00, or you can
7 large pizzas for $ Which is the better
buy?
$10.00 / 4 = $2.50/1
$19.25 / 7 = $2.75/1
It is cheaper to buy 4 pizzas.