**RATIO & PROPORTION, PERCENTAGE & AVERAGES**

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**Ratio & Proportion**

A proportion is a name we give to a statement that two ratios are equal. It can be written in two ways:

- two equal fractions,

or

- using a colon,
**a:b = c:d**

When two ratios are equal, then the cross products of the ratios are equal.

That is, for the proportion, **a:b = c:d , a**** **x** ****d = b**** **x** ****c **

**Percent:**

Percent to fraction: x% = x/100

Percentage formula: Rate/100 = Percentage/base

Rate: The percent.

Base: The amount you are taking the percent of.

Percentage: The answer obtained by multiplying the base by the rate

Average:

Let a_{1},a_{2},a_{3},……,a_{n} be a set of numbers, average = (a_{1} + a_{2} + a_{3},+……+ a_{n})/n