**CAT , GMAT , GRE , MBA**

Ratios

Ratios look like fractions and are related to fractions. Whereas a fraction describes a part of a whole, a ratio compares two parts.

The ratio of a to b may be written in different ways such as a to b, or a : b, or a ÷ b, or a / b where b not equal to 0

Proportions

A proportion is a statement that show equality between two ratios .

The proportion a / b = c / d may be written in different ways such as a : b = c : d, or a : b :: c : d (read as 'a is to b as c is to d').

The terms on the outside, a and d, are called the extremes and the terms on the inside, b and c, are called the means.

Since a : b and c : d are ratios, b and d are nonzero.

On multiplying each side of the proportion by b d, the proportion becomes equivalent to the equation a d = b c.

In a proportion, the product of the extremes equals the product of the means.