A ratio is a comparison of two or more numbers that are usually of the same type or measurement. If the numbers have different units, it is important to convert the units to be the same before doing any calculations.

A proportion is a name we give to a statement that two ratios are equal.In proportion, the first and fourth terms are called extremes and the second and third terms are called means.

A percentage is a number or rate that is expressed as a certain number of parts of something divided into 100 parts. It is often denoted using the percentage sign " % ".