1. Ratios
Dittamo Lewis Notes 2012

2. When you have a ratio, it DOESN’T MATTER if your fraction is improper!
Ratios
A ratio is the comparison of two numbers written as a fraction.
For example:
Your school’s basketball team has won 7 games and lost 3 games. What is the ratio of wins to losses?
Because we are comparing wins to losses the first number in our ratio should be the number of wins and the second number is the number of losses.
The ratio is
___________
games won
_______
7 games __ 7 = =
When you have a ratio, it DOESN’T MATTER if your fraction is improper!
games lost
3 games 3

3. WRITE RATIOS AS FRACTIONS IN SIMPLEST FORM
A ratio is a comparison of two numbers by division. If a gallon of paint contains 2 parts blue paint and 4 parts yellow paint, then the ratio comparing the blue paint to the yellow paint can be written as one of the following 3 ways.
Recall that a fraction bar represents division. This is the most common method to write ratios. If necessary, ALWAYS simplify the ratio.

4. 1 Example Write Ratios as Fractions
Express the ratio 9 goldfish out of 15 fish as a fraction in simplest form.
How can we reduce
This fraction?
Goldfish
Fish
The ratio of goldfish to fish is 3 to 5. This means that for every 5 fish, 3 of them are goldfish.

5. How can we reduce this fraction?2
Example
Write Ratios as Fractions
Express the ratio 15 dimes out of 24 coins as a fraction in simplest form.
How can we reduce this fraction?
Dimes
Coins
The ratio of dimes to coins is 5 to 8. This means that for every 8 coins, 5 of them are dimes.

6. 3 Example Write Ratios as Fractions
When writing a ratio involving measurements, both quantities should have the same unit of measure. 3
Example
Write Ratios as Fractions
Express the ratio 3 feet to 16 inches as a fraction in simplest form.
How do we reduce
This fraction?
Remember to convert feet into inches, multiply by 12.

7. 4 Example Write Ratios as Fractions
Express the ratio 10 inches to 3 feet as a fraction in simplest form.
Remember to convert feet into inches, multiply by 12.
How do we reduce
this fraction?

8. Cross-Multiply! 3 5 18 30 = Any ideas??? =90 =90
Sometimes you will be given two ratios and asked to determine if they are equal
Any ideas???
Since ratios can be represented as fractions, you can compare them the same way you compare fractions!
Cross-Multiply!
=90
=90 3 5 18 30
These ratios
are equal! =