Proportional Reasoning

Section 2.3

Objectives:

To solve problems using proportional reasoning.

Use more than one method to solve proportional reasoning problems.

What Is A Proportion?

Proportions are two ratios set equal to each other

Example:

How Do You Know If A Proportion Is True?

The cross-products of the ratios must be equal.

Ex.

Cross-Product…

4 x 10 = 40 and 5 x 8 = 40

It is a proportion!

Proportions & Variables

Proportions may contain a variable.

Example:

Solving Proportions That Contain Variables

To solve for the variable you… CROSS MULTIPLY

Step 1

Step 2

Step 3

Step 4

Step 5

Your Turn…

Solve the following proportion:

Word Problems Using Proportions

There is a ratio of 8 boys to 12 girls in a classroom. How many girls would there be if there were 12 boys in the classroom?

Homework

2.3 Proportions Worksheet