## GMAT Quantitative Review

**3.0**** ****Math Review**

**3.1 Arithmetic**

**5. Ratio and Proportion**

The *ratio* of the number *a* to the number *b* .

A ratio may be expressed or represented in several ways. For example, the ratio of 2 to 3 can be written as 2 to 3, 2:3, or . The order of the terms of a ratio is important. For example, the ratio of the number of months with exactly 30 days to the number with exactly 31 days is , not .

A *proportion* is a statement that two ratios are equal; for example, is a proportion. One way to solve a proportion involving an unknown is to cross multiply, obtaining a new equality. For example, to solve for *n* in the proportion , cross multiply, obtaining ; then divide both sides by 3, to get .