Place holders
Look at the number 4 040. How much is it worth?
| thousands | hundreds | tens | units (ones) |
| 4 | 0 | 4 | 0 |
This number is four thousand and forty. We must use zeros to keep the digits in the correct columns. If we missed out the zeros from the number above we would have 44 and that is a very different number from 4 040.
44 = four tens and four units
| thousands | hundreds | tens | units (ones) |
| | | 4 | 4 |
4 040 is much bigger than 44.
4 040 = four thousands, no hundreds, four tens and no units
| thousands | hundreds | tens | units (ones) |
| 4 | 0 | 4 | 0 |
Both the fours and the zeros are important in this number. Zero is called a place holder. It is not worth anything on its own, but it changes the value of other digits. In this case zeros change the number 44 to the much larger number 4 040.
The digit on the right of any number must always go into the units column. If there are no units there will be a zero. For example in the number 20 there is a zero in the units place.
| thousands | hundreds | tens | units (ones) |
| 0 | 0 | 2 | 0 |
