Adult Literacy Fundamental Mathematics VI

Introduction to Ratios

Ratio is a comparison of one number or quantity with another number or quantity. Ratio shows the relationship between the quantities.

Ratio is pronounced “rā’shō” or it can be pronounced “rā’shēō.” Check out this YouTube video to listen to someone pronouce the word: How to Pronounce Ratio.

You often use ratios, look at these examples:

• Scores in games are ratios. For example, the Penguins won 4 to 3 or the Canucks lost 1 to 5.
• Directions for mixing can be ratios. For example, use 1 egg to each cup of milk or mix 25 parts gas to 1 part oil for the motorcycle.
• Betting odds are given as ratios. For example, Black Jade is a 3 to 1 favourite or the heavyweight contender is only given a 2 to 5 chance to win.
• The scale at the bottom of maps is a ratio. For example, 1 centimetre represents 10 kilometres.
• Prices are often given as ratios. For example, 100 grams for $0.79 or 2 cans for $1.85.

For ratios to have meaning you must know what is being compared and the units that are being used. Read these examples of ratios and the units that are used. A general ratio may say “parts” for the units.

Topic C- Proportion

A proportion is a statement that two ratios are equal or equivalent.

Proportions can be used to solve many math problems. You will soon learn to use proportions to solve problems involving percent. The techniques you practice in the next few pages are important for that problem solving work.

Problems often give incomplete information; that is, one of the terms is missing. To solve such problems, you first find the comparison or ratio that is given. It may be:

• A quantity of one thing that is mixed with a larger quantity of something else
• A scale of measurement given on a map such as 1 cm on the map represents 100 km distance on land
• Cost for a certain number of items
• Time to travel a certain distance

The problem will then give one term of the second ratio in the proportion. For example, if you have been told that 3 heads of lettuce cost $1.49, you may be asked to find the cost of 7 heads of lettuce.