Let's review what we know about five- and six-digit whole numbers. These are thousands numbers, and they include a comma.
When we read a thousands number, we say the number before the comma first, and then we say "thousand." Then we read the number after the comma. How would you say the number 15,426? It would be read as fifteen thousand, four hundred twenty-six. What about the number 684,000? You would say this as six hundred eighty-four thousand.
If you know how to read a thousands number, you can figure out where to place a comma in the number. Take a look at this example:
410392
This thousands number is missing a comma. To figure out where the comma goes, we need to find the ones place, the tens place, and the hundreds place (also called the ones column, tens column, and hundreds column). Start by looking on the right-hand side of the number. What digit is in the ones place? It is 2. What digit is in the tens place? The tens digit is 9. What digit is in the hundreds place? The digit is 3.
Now that we have found those, what digits are left? The digits left are 4, 1, and 0. These must tell us about thousands. Add a comma after this part of the number. We've figured out that the number should be written as 410,392.
