The term percent means out of a hundred. In mathematics, percentages are used like fractions and decimals, as ways to describe parts of a whole.  When you are using percentages, the whole is considered to be made up of a hundred equal parts. The symbol % is used to show that a number is a percentage.

 

It is easy to work out the percentage when there are 100 individual ?things? making up the whole. But what if there are more or less?

 

The answer is that you convert the individual elements that make up the whole into a percentage.

 

This is easiest to understand with an example. Suppose that you want to buy a new laptop, and you found your local store will give you 20% off the list price of $500. How much will the laptop cost after the discount?

 

In this example, the whole is $500, and the percentage that you need to find is 20%.

 

Start by working out the value of 1% of $500, which is 500 / 100 = $5.

 

Now you multiply the value of 1% by the percentage you are looking for, in this case 20%: $5 x 20 = $100.

 

So now you know the discount is $100. So the cost after the discount will be $500 - $100 = $400.

 

Now let us use an example to see how to calculate percentage changes.

 

Suppose: your parent wants you to increase your math test score from 80 (current number) to 90 (new number). How much of a percentage increase is it?

 

To find out, you first find the absolute increase:

 

Absolute increase = new number - current number = 90 - 80 = 10.

 

Then you divide the increase by the current number, and then multiply the answer by 100:

 

Percentage increase = (absolute increase / current number) x 100 = (10/80) x 100 = 12.5%

 

Now let us see how to calculate percentage decrease.

 

Suppose your parent want you to cut down on your weekly expenses from $50 (current number) to $40 (new number). How much of a percentage decrease is it?

 

To find out, you first calculate the absolute decrease between the two numbers you are comparing:

 

Absolute decrease = Current Number - New Number =  50 - 40 = 10.

 

Then you divide the decrease by the current number and multiply the answer by 100:

 

Percentage decrease = (absolute decrease / current number) x 100 = (10/50) x 100 = 20 %