These flasks hold .125 of a liter or one hundred twenty-five milliliters.

Decimals on the Right

Let's start by talking about what a decimal looks like. A decimal is a number that has a decimal point somewhere in the number. That makes sense. A decimal point is a dot, period, spot, or smudge. The number could look like these:
1.2
1.23
1.234
1.2345
1.234567890123456789

See how there are numbers on the left and right side of the point? The numbers on the left side represent whole numbers such as ones, tens, hundreds, and thousands. The numbers on the right side of the point are the decimal values. Those numbers represent values called tenths, hundredths, thousandths, and so on. The naming difference is in the "th". Tenths are the closest value to the point. There are no "oneths."

Breaking it Down Into Tens

You've noticed how the numbers before and after the point use the same symbols. In the same way that our whole number system is based on tens, the decimal system is also based on tens. For example, there are ten tenths in a whole number. There are ten hundredths to every tenth. It goes on like that.

The tenths are the largest amount in the decimal system. As the "th" values get longer names the values is smaller. For example, four hundred thousandths is a much smaller number than four hundredths.

Fractions and Decimals

Fractions and decimals are related because the both describe values that are smaller than one. If you look at a fraction as one number divided by another, the quotient is the decimal number. Here are simple and complex examples: 1/4 is one quarter.
1 divided by 4 is equal to 0.25.
0.25 is the decimal equivalent to 1/4.

36/288 is one complex fraction.
36 divided by 288 is equal to 0.125.
0.125 is the decimal equivalent to 36/288.

RELATED ACTIVITIES

Adding Tenths on a Number Line
- Play Activity

Identify Thousandth Values
- Play Activity

While you still buy pints of milk, you regularly buy 2-liter bottles.

The Metric System

The metric system is a measuring system we use some of the time in the United States. Other countries across the world use the system for everything. The metric system is based on tens and uses decimals all of the time. You will learn about the system in school math classes and eventually science classes. While the metric system is super-easy to understand, it is a bit difficult to switch from the U.S traditional English system of measurements. Here are some examples of metric values that use decimals.

A kilometer is one thousand (1,000) meters. Five hundred (500) meters is 0.5 of a kilometer.
A liter is one thousand (1,000) milliliters. A two-liter bottle holds 2,000 milliliters.

Compare those metric numbers to values we sometimes use.

A mile is one thousand seven hundred sixty (1,760) yards. Eight hundred eighty (880) yards is 0.5 of a mile.
A gallon is one hundred twenty-eight (128) fluid ounces. A two-gallon bottle of water holds two hundred fifty-six (256) fluid ounces.

See how it's easier to do the math when everything uses a counting base of ten? We'll cover the metric system in a later section. Just remember that the metric system uses decimals all of the time.

Think about the two systems before you do more decimals stuff. Why do you ask for a pound and a half of meat at the store instead of twenty-four (24) ounces? Do you think the person working behind the counter would know how much twenty-four ounces is? Try it and see if you get the right amount of food. Do you think it might be easier to ask for five hundred grams meat is if everyone knows a kilogram is one thousand grams?

RELATED ACTIVITIES

Comparing the Sums of Simple Decimals
- Play Activity

Subtracting Decimals with Tenths
- Play Activity

RELATED LINKS

- Numbernut: Basic Math
- Numbernut: Prealgebra
- Biology4Kids: Scientific Method
- Biology4Kids: Logic

-	Overview
-	Number Types
-	Fractions
>	Decimals
-	Percentages
-	Estimates & Rounding
-	Ratios
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