Ratio, Rate, Unit Rate, and Proportions

This past week we have been discussing how to simplify a ratio, and to identify a rate, how to find a unit rate, and how to find the missing value in a proportion.

A ratio is a comparison of 2 like quantities.  Ratios need to be in simplest form and they can be written 3 different ways.

Example:


This ratio can be written as 1:3, 1 to 3, or as a fraction 1/3.

A rate is a ratio that compares quantities of different units.
A unit rate is a comparison of a quantity to 1.

Example:

Unit rates become very important when doing price comparison.  We always want to get the best buy.

Example:

    

Which flash drive is the best buy?

5.99/8 = $0.75 per GB                                                         24.95/64 = $0.39

The 64 GB hard drive, according to price, is the better flash drive.

A proportion states that two ratios that are equal to each other.  To solve a proportion you find the cross products and solve for the missing variable by dividing.

Example:

Images from Google.