Percentages have been used since the late 17th century to calculate taxes, interest, income and losses, among other things. The idea of ​​the percent, however, dates back to the Roman emperor Augustus (63 BC - 14 AD). He ordered the payment of a tax on all auctioned items, which was to always be one hundreth of the price at which the item was sold. The name "percent" comes from the Latin words per centum, "per hundred" or pro centum, "one hundred".

A percentage that is marked as a decimal or a fraction is called a percentage factor. The percent is obtained from the percentage factor by moving the decimal point two steps to the right. Usually, percents are used in answers and assignments, whereas the calculations themselves are performed using percentage factors.

Example 1

Convert

a) the percent value to a decimal number.

[[$ \quad 62 \: \% = \displaystyle\frac {62} {100} = 0,62 $]]​

b) the fraction to a percent value.

NB! In practice, fractions are converted to percents by performing a division calculation with a calculator and multiplying the resulting decimal by [[$ 100 \: \% $]]​, as in example 2.

Example 2

Lina has [[$ 24 $]]​ Facebook friends on her list, [[$ 6 $]]​ of whom are foreigners. Calculate how many percent of Lina's Facebook friends are foreigners?



Answer: [[$ 25 \: \% $]]​ of Lina's Facebook friends are foreigners.