Writing Numbers as Words/Numerals (Decimals)

When we move to the right of the decimal in the base-10 system, we use almost the same process to name numbers as we do when naming numbers to the left of the decimal, but in reverse.  One key difference: The first place value to the right of the decimal is the tenths place.  There is no "oneths" place.  Essentially, although we think of the numberline folding over on itself (and having mirror images) on the decimal point, it actually folds over on the ones place.  If you think of the ones places as the middle between tens and tenths, hundreds and hundredths, etc, it makes sense.  The ones place is the pivot point.  When the numbers get bigger, 1 is multiplied by 10s (1x10 = tens place, 1x100=hundreds place).  When the numbers get smaller, they are divided by 10 (1$\div$ 10= $\dfrac{1}{10}$, 1$\div$ 100= $\dfrac{1}{100})$.

In order to name decimals students still need to know the names of the ones place words...

and the tens place words.

Students also need to know the place value names of the decimal places (which follow a pattern very similar to the place names to the left of the decimal). 

From there, naming a decimal just means reading the number that is to the right of the decimal (just imagine that the decimal is not there, following the rules for naming regular numbers), and then saying the decimal place value that the number ends in. 

Example:

.33 = thirty three hundredths

.079 = seventy nine thousandths

.0801 = eight hundred one ten thousandths

When there is a whole number and a decimal, read the whole number, say and, and then say the decimal number. 

4.45 = four and forty-five hundredths

13.07919 = thirteen and seven thousand nine hundred nineteen hundred thousandths

2,309.0804501 = 2 thousand three hundred nine and eight hundred four thousand five hundred one hundred millionths