Introduction to Ratio, Proportion and Similarity


Introduction to

Ratio, Proportion, and


Overview for the topic:

- learn how to write and simplify ratios

- learn how to determine whether two ratios are a proportion and how to use proportions to solve problems learn how to determine whether two triangles are similar

What is a


A ratio is the comparison of two numbers using division.

The ratio of x to y can be written or x:y.

Ratios are usually expressed in simplest form.

What is a


Since 2/4 and 3/6 are both equal to 1/2, they are equal to each other.

A statement that two ratios are equal is called a proportion.

A proportion can be written in one of the following ways:

2/4 =3/6 or 2:4 = 3:6

The first and last numbers in a proportion are called the extremes.

The middle numbers are called the means.


Means-Extremes Property

In a proportion, the product of the means equals the product of the extremes.


Triangle Similarity

Two figures are similar if you can show that the following two statements are true:

1. Corresponding angles are congruent.

2. Corresponding sides are in proportion.