Solve Proportions

**Solve Proportions**

**True Proportions**

- A proportion is an expression of the equality of two ratios or rates.
- A proportion is true if the fractions are equal when written in lowest terms.

Example

*when units are used, the units of the numerators are the same, and the units of the denominators are the same.*) Also, in any true proportion, the "cross products" are equal.

The cross products

*ad*and*bc*are obtained from the proportionWe know that 3 12 = 4 9 from the proportion

**Solving Proportions**

Sometimes one of the numbers in a proportion is unknown. In this case, it is necessary to solve the proportion.

To solve the proportion, find a number to replace the unknown so that the proportion is true. You can use cross-products to solve a proportion.

Example

Find n on the following proportion

**Solution**