The concept of a percent
The term "percent" (also written as "per cent") is derived from the Latin word "per centum", which means, "by the hundred". Indeed, a percentage expresses a ratio, which is expressed as a fraction of 100. Mathematically speaking,
that is,
Using this definition, we can convert percentages to decimal numbers, or vice versa.
Example 1
Convert 0,072 and into percentages.
Solution: To convert decimal numbers into percentages, we multiply by 100. This principally moves the decimal separator two steps to the right. Therefore,
To convert into a percentage, we first convert the fraction into a decimal number. That is, . Finally, we multiply the decimal number by 100:
Example 2
Convert 42,3% and 0,12% into decimal numbers.
Solution: To convert percentages into decimal numbers, we divide by 100. This principally moves the decimal separator two steps to the left, so
Similarly,