Percentages (%)
When you say "Percent" you are really saying "per 100"
So 50% means 50 per 100 (50% of this box is green)  And 25% means 25 per 100 (25% of this box is green)  
Examples:
100% means all.
Example:
100% of 80 is ^{100}/_{100} × 80 = 80
 
50% means half.
Example:
50% of 80 is ^{50}/_{100} × 80 = 40
 
5% means ^{5}/_{100ths}.
Example:
5% of 80 is ^{5}/_{100} × 80 = 4

Using Percent
Because "Percent" means "per 100" you should think "this should always be divided by 100"
So 75% really means ^{75}/_{100}
And 100% is ^{100}/_{100}, or exactly 1 (100% of any number is just the number, unchanged)
And 200% is ^{200}/_{100}, or exactly 2 (200% of any number is twice the number)
Use the slider on the left and try some different numbers (example, what is 40% of 80?)

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

Read more about this at Decimals, Fractions and Percentages.
Some Worked Examples
Example: Calculate 25% of 80
25% = ^{25}/_{100}
(^{25}/_{100}) × 80 = 20
So 25% of 80 is 20
Example: 15% of 200 apples were bad. How many apples were bad?
15% = ^{15}/_{100}
(^{15}/_{100}) × 200 = 15 × 2 = 30 apples
30 apples were bad
Example: if only 10 of the 200 apples were bad, what percent is that?
As a fraction, 10/200 = 0.05
As a percentage it is: (10/200) x 100 = 5%
5% of those apples were bad
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% = ^{25}/_{100}
(^{25}/_{100}) × $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
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.
No comments:
Post a Comment