**Ratios & Proportions**

Units

Can you compare apples to oranges?

Writing Ratios

There is a specific way that you must write ratios

Ratio

**A comparison between two numbers or items**

2 girls

1 boy

4 apples

23 pieces of fruit

Proportion

- An equation containing two ratios that are equal

1

2

2

4

=

2:1

4:23

You can use Cross Multiplication to see if the two are proportional

1

3

9

3

3(3) = 1(9)

9 = 9

These ratios are proportional

So what happens when we don't know one of the numbers in a proportion?

x

4

12

16

=

What is the second key concept?

Hint...

Solve proportions by using Cross Multiplication

2 to 1

4 to 23

Three ways to express ratios:

1. Using the word "to"

2. Using a colon":"

3. As a fraction

Example:

Write the ratio of girls to boys in this classroom

Can you compare seconds to miles?

Proportions are always written using units of measurement that are of the same type

Examples:

Centimeters

Meters

Miles

Yards

Seconds

Minutes

Hours

Days

Cups

Pints

Gallons

Quarts

Pounds

Kilograms

Grams

Ounces

Weight:

Liquids:

Time:

Length:

1

3

3

9

=

=

?

?

Write the ratio of ties to bow ties

Now let's look at this proportion.....

x+3

2

=

15

6

4 fingers

2 hands

8 fingers

1 hand

=

must be in the same units

must be in the same units

**Exit Slip**

**Compute the difference between the salaries from 1967 to 2010.**

Write a reflection about the observation that you made

Write a reflection about the observation that you made