It is important to know when a zero is a placeholder, and when it is a leading zero. Although the digit 0 adds no value to a number, it generally acts as a placeholder to keep the other digits in their proper places. For example, the number 5,001,000 breaks down into 5,000,000 + 1,000. Suppose, however, you decide to leave all the 0s out of the chart. Here is what you’d get:
| Hundred Millions | * |
| Ten Millions | * |
| Millions | * |
| Hundred Thousands | * |
| Ten Thousands | * |
| Thousands | * |
| Hundreds | * |
| Tens | 5 |
| Ones | 1 |
This tells you that 5,001,000 = 50 + 1. Clearly, this answer is wrong!
As a rule, when a 0 appears to the right of at least one digit other than 0, it’s a placeholder. Place-holding zeros are important — always include them when you write a number. However, when a 0 appears to the left of every digit other than 0, it’s a leading zero. Leading zeros serve no purpose in a number, so dropping them is customary. For example, place the number 003,040,070:
| Hundred Millions | 0 |
| Ten Millions | 0 |
| Millions | 3 |
| Hundred Thousands | 0 |
| Ten Thousands | 4 |
| Thousands | 0 |
| Hundreds | 0 |
| Tens | 7 |
| Ones | 0 |
The first two 0s in the number are leading zeros because they appear to the left of the 3. You can drop these 0s from the number, leaving you with 3,040,070. The remaining 0s are all to the right of the 3, so they’re placeholders — be sure to write them in.