A ratio is a way to compare two or more objects of the same type.  When two ratios are equal, they are said to be in proportion. The most common ways that a ratio is written is either as a fraction or using the ratio symbol.  Both ways can be used, for example

In this example, the fraction 5/7 can be written in the form 5:7 (we say this as 5 is to 7).

Often we are ask to divide quantities in a certain ratio.  As an example, you may be asked to divide $20 in the ratio 3:7 for some reason, maybe to share some profit you made selling slide rule secrets.

Since the ratio is 3:7, this means that I must have 10 equal parts altogether (3 + 7 = 10).  If I divide $20 into 10 equal parts, then each part must be equal to $2.  So I have 3 equal parts is to 7 equal parts

3 x $2 : 7 x $2 = $6 : $14

When this is written

3 : 7 = $6 : $14

we have what is known as a statement of proportion.

Let's check out some questions involving ratio and proportion!