Decimals for Kids: Learning the Decimal System

Understanding Decimals

Decimals are another way to write fractions and mixed numbers. Decimals use a decimal point, which is just a period, to separate the 'whole' part of the number from the 'fractional' part of the number. The whole number part goes to the left of the decimal point, and the fractional part goes on the right side of the decimal point.

Place Values

You've probably already learned that whole numbers have place values, like the ones place, the tens place and the hundreds place. For instance, in the number 357, the three is in the hundreds place, the five is in the tens place and the seven is in the ones place. Whole numbers can be written as decimals by adding a decimal point and a zero, like this: 357.0.

Decimal Places

To understand decimal places, imagine that you're measuring two lengths of wood, and both lengths are between 357 centimeters and 358 centimeters. However, they're not exactly the same length. If you were measuring the lengths of wood in inches, you'd report their lengths using a mixed number, like 140 1/4 inches or 140 3/8 inches. When you're working with metric units, like centimeters, you replace these mixed fractions with decimals.

Tenths

The numbers to the right of a decimal point always represent amounts that are less than one whole unit. In the example with the lengths of wood, these numbers represent fractions of a centimeter. The first number to the right of the decimal always represents a fraction of ten, so this place is called the tenths place. For instance, the fraction 1/10 would be written as 0.1, and the fraction 7/10 would be written as 0.7. If one of the two lengths of wood were 357 and 1/10 of a centimeter, this would be written as the decimal 357.1.

Hundredths

Now, imagine that the two lengths of wood are both between 357.1 and 357.2 centimeters. However, one is still a tiny bit longer than the other. To represent this difference, you need to use the second decimal place to the right of the decimal point, the hundredths place. Decimals that extend to the hundredths place represent a fraction of 100. For instance, 7/100 would be 0.07, and 73/100 would be 0.73. If one of the lengths of wood were 357 and 11/100 of a centimeter, the decimal would be 357.11.

Thousandths

The thousandths place, which is the third place to the right of the decimal point, represents thousandths of a unit. For instance, 9/1000 of centimeter would be 0.009, and 999/1000 of a centimeter would be 0.999. If both of your lengths of wood were between 357.11 and 357.12 centimeters, but still not exactly the same length, you'd need to measure them to the thousandth of a centimeter. For instance, one of them might be 357 and 117/1,000 of a centimeter, which would be written as 357.117 cm.