**Many people use decimals every day when they deal with money.** Decimals are also commonly found on gas pumps and on a car's odometer. All these uses of decimals are a way to show a fraction of a whole unit, such as a dollar or gallon of gasoline.

Every time someone buys an item and makes change, they are working with decimals. In addition many stores price items at $1.99, or similar, because $1.99 seems like less money than $2. This is because people consider the number on the left side of the decimal to be more important.

Decimal numbering, which is numbering based on sets of 10, came from ancient civilizations such as the Romans'. Today Arabic numerals are more commonly used then Roman numerals, but they still use decimal numbering. In 1616, John Napier, a Scottish mathematician, suggested that decimal numbering could be used to represent fractions if a decimal point were added. Numbers on the left side of the point would be whole numbers, and those on the right would show the fraction. To determine what decimal numbers represent the fraction, the top number of the fraction is divided by the bottom number. This means that one-half becomes 0.5, and one-quarter becomes 0.25.