# Percentage

## Percentage

Ratio in which the second term is 100.

### Symbol

The symbol “%” means “divided by 100” and is read as “percent”.
When writing a percentage in English, we do not leave a space between the number and the percentage symbol.

A percentage is a specific kind of ratio, which is a comparison between two sizes or quantities of the same type.
Generally, a percentage does not exceed one hundred percent; however, there are situations where this can be appropriate:

• An investment made a profit of 124%.
• This house was assessed at 115% of its actual value.

### Examples

The expressions $$\dfrac {12} {100}$$ and 12 % both express percentages.

### Educational Note

In practice, a percentage is a denominate number, because we always talk about the percentage of something.

This means that operating on percentages would be an incorrect practice, although it is permitted in certain contexts.

This means that operating on percentages would be an incorrect practice, although it is permitted in certain contexts.
Writing 20% + 10% = 30% only means something if all these percentages apply to the same quantity. In the case of mixing ingredients, for example, operations on percentages that express weights cannot be added, because 0.5 litres of cream with 15% fat content added to 1 litre of cream with 10% fat content does not make a product that is 25% fat content! However, if these percentages apply to the same quantity, they can be added as fractions with denominators of 100: 10% of the books and + 20% of the books does result in 30% of the books (10% + 20% = 30%).

### Historical Note

The percentage symbol appeared for the first time in 1425 in an Italian manuscript of unknown origin. The symbol used was a bit different from the one we use today. In the end, it wasn’t until around 1650 that the symbol used became $$\frac{0}{0}$$. Then, later, the horizontal bar became slanted to make the symbol % that we use today.