Definitions:
A ratio is an ordered pair of numbers a and b, written a / b where b does not equal 0.
A proportion is an equation in which two ratios are set equal to each other.
For example, if there is 1 boy and 3 girls you could write the ratio as:
- 1 : 3 (for every one boy there are 3 girls)
- 1 / 4 are boys and 3 / 4 are girls
- 0.25 are boys (by dividing 1 by 4)
- 25% are boys (0.25 as a percentage)