GMAT Quantitative Review

3.0 Math Review

3.1 Arithmetic

5. Ratio and Proportion

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

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 image. 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 image, not image.

proportion is a statement that two ratios are equal; for example, image 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 image, cross multiply, obtaining image; then divide both sides by 3, to get image.