When we say "Percent" we are really saying "per 100"

One percent (1%) means 1 per 100.
1 in 100
1% of this line is shaded green: it is very small isn't it?

grid 50 of 100 equals 50%50% means 50 per 100
(50% of this box is green)

 
25% means 25 per 100
(25% of this box is green)
grid 25 of 100 equals 25%
 

Examples:

grid 100 of 100 equals 100% 
100% means all.
Example:
100% of 80 is 100100 × 80 = 80
grid 50 of 100 equals 50% 
50% means half.
Example:
50% of 80 is 50100 × 80 = 40
grid 5 of 100 equals 5% 
5% means 5/100ths.
Example:5% of 80 is 
5100 × 80 = 4So 75% really means 
75100
And 100% is 100100, or exactly 1 (100% of any number is just the number, unchanged)
And 200% is 200100, or exactly 2 (200% of any number is twice the number)

A Percent can also be expressed as a Decimal or a Fraction


pie 1/2 
A Half can be written... 
  
As a percentage:
50%
As a decimal:
0.5
As a fraction:
1/2
Read more about this at Decimals, Fractions and Percentages.

Some Worked Examples

Example: Calculate 25% of 80

25% = 25100
And  25100 × 80 = 20
So 25% of 80 is 20

Example: 15% of 200 apples are bad. How many apples are bad?

15% = 15100
And  15100 × 200 =  15 × 200100 
  =  15 × 2  
  =  30 apples
30 apples are bad

Example: if only 10 of the 200 apples are bad, what percent is that?

As a fraction, 10200 = 0.05
As a percentage it is: 10200 x 100 = 5%

5% of those apples are bad
skateboard

Example: A Skateboard is reduced 25% in price in a sale.
The old price was $120.
Find the new price.


First, find 25% of $120:
25% = 25100
And  25100 × $120 = $30
25% of $120 is $30
So the reduction is $30

Take the reduction from the original price
$120 − $30 = $90
The Price of the Skateboard in the sale is $90

Calculation Trick

This little rule can make some calculations easier:
x% of y = y% of x

Example: 8% of 50

8% of 50 is the same as 50% of 8
And 50% of 8 is 4
So 8% of 50 is also 4

The Word

"Percent" comes from the latin Per Centum. The latin word Centum means 100, for example a Century is 100 years.

Percent vs Percentage

My Dictionary says "Percentage" is the "result obtained by multiplying a quantity by a percent". So 10 percent of 50 apples is 5 apples: the 5 apples is the percentage.
But in practice people use both words the same way.

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