Percentages

In mathematics, a

# percentage

is a way of expressing a number as a fraction of 100 (*per centum*meaning “per hundred” in Latin). It is often denoted using the percent sign, “%”, or the abbreviation “pct”. For example, 45% (read as “forty-five percent”) is equal to 45/100, or 0.45.

*There are 3 main types of percentage problems:*

*When you need find the number corresponding to the percentage from original number. In this case you need the original number multiply by the percent and divide by 100.*

**Example:**

Find 25% of 10 (remember ‘of’ means ‘times’).

**Solution :**

25 *10 / 100 =2.5

*When they give you the percentage and the number which corresponded to this percentage and you need to find the original . In this case problem are solving by DEVISION by this percentage and then multiply by 100.*

**Example:**

2 5% of a certain number is 15. What is the number?

**Solution :**

Following our rule:

15 / 25 * 100 = 60

*When you need to find what percentage one number is of another. In order to solve this problem we need second number divide by first one and then result multiply by 100.*

**Example:**

What percent of 1 hour is 15 minutes?

**Solution :**

First of all noticed that we need use the same units so let convert hours to the minutes 1 hour = 60 min, and then following our rule :

15/ 60 *100 = 25 %