Ratios and Unit Rates
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 “ : ”
Examples:
• Four out of five dentists surveyed
recommend sugarless gum for their
patients who chew gum
4
4 to 5 4:5
5
• 9 people out of 20 like chocolate ice cream
9
9 to 20 9:20
20
In a class of thirty students,
thirteen are boys. Write a ratio
for the number of boys to
students in the class.
13/30
13 to 30
13:30
Write a ratio for the number of
boys to the number of girls.
13/17
13 to 17
13:17
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 3
40:60 = 2:3
6 freethrows made out of 10 attempts
6/10 = 3/5
3 to 5
3:5
24 questions correct on a 100-question test
24/100 = 6/25
6 to 25
6 : 25
5 cookies eaten out of 20 cookies
5/20 = ¼
1 to 4
1:4
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
Examples:
You need to buy soda for a party.
The store sells 3 12-packs for
$7.80. Find the unit rate for one
12-pack?
$7.80/3 = $2.60/1
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
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 $19.25. Which is the better
buy?
$10.00 / 4 = $2.50/1
$19.25 / 7 = $2.75/1
It is cheaper to buy 4 pizzas.