Chapter 6 Review

• A ratio compares 2 quantities.

• There are three ways to write a ratio: • For example: The ratio of boys to girls in the class is: 11 to 9 11:9 11 This means that there are 9 11 boys and 9 girls in our

class.

• Example 1- 14 dogs to 10 cats.____________ _______________ _______________

• Example 2- 36 shoes to 18 socks.____________ _______________ ________________

A ratio is called a rate when the units of measure of the quantities are different. A rate shows how quantities with different units are related to each other. • An example of a rate would be: 40 points 5 games

• You read the rate as “40 points per 5 games” or “40 points in 5 games.”

• When the second quantity in a rate is 1 unit, it’s called unit rate.

• Example: Write the expressions a rate. Then express each rate as a unit rate.

$12.00 for 3 notebooks =

• $12.00 = $4.00 3 notebooks 1 notebook • A unit price is a unit rate that gives us the cost of 1 item.

Equivalent Ratios and Rate, just like equivalent fractions, you must multiply or divide the numerator and denominator of a given ratio or rate by the same number.

For example the ratio: 3bones is equivalent to 6 bones 1 ear 2 ears

Ex: Find two ratios equivalent to 9 ( you must multiply and15 divide the numerator and

the denominator by the same number. )

Multiply: Divide: 9 = ×2 = 18 9 = ÷3 = 3 15 ×2 30 15 ÷3 5

You can also create a table of equivalent ratios or rates, just use the same method you used when doing equivalent fractions.

• For example: Complete the table to create four ratios equivalent to 4

9

• ×2 ×3 ×4

×5jjjj

4 8 12 16 20

9 18 27 36 45

2

5

Your Example: Complete the table to create 4 equivalent ratios.

A proportion is an equation or statement that shows two ratios are equal. One way to check if if two ratios are proportional (or equivalent), you can reduce each ratio to lowest terms and see if they are equal. Another way to see if two ratios are proportional is to cross multiply. This way you multiply the numerator of one ratio with the denominator of the other ratio. If the products are equal, they form a proportion.

You can use cross multiplication to find an unknown number in a proportion (a variable.)