Three-digit numbers can be written in expanded form to show the value of each digit. For example, 234 = 200 + 30 + 4. This makes clear that the 2 represents 200, not just 2.
You already understand that three-digit numbers have a hundreds place, a tens place, and a ones place. Expanded form is simply a way of writing a number so that the full value of each digit is visible, rather than compressed into a single string. Writing 234 as 200 + 30 + 4 unpacks the number: the 2 is worth two hundred, the 3 is worth thirty, and the 4 is worth four.
The value of a digit depends entirely on its position. The same digit 5 means something completely different depending on where it sits: 5 in the ones place is just five, but 5 in the tens place is fifty, and 5 in the hundreds place is five hundred. Expanded form makes these hidden positional values explicit by writing them out as separate addends.
A useful way to build expanded form is to identify each digit and multiply it by its place value: 2 is in the hundreds place, so its value is 2 × 100 = 200. The 3 is in the tens place, so its value is 3 × 10 = 30. The 4 is in the ones place, so its value is 4 × 1 = 4. Writing all three gives the expanded form: 200 + 30 + 4. Going the other direction — collapsing expanded form back into a number — is simply addition: 200 + 30 + 4 = 234.
Expanded form is not just a notation exercise. It is the foundation of how multi-digit addition and subtraction work. When you add 234 + 153, you are really adding 200 + 100 = 300 in the hundreds, 30 + 50 = 80 in the tens, and 4 + 3 = 7 in the ones, then combining: 300 + 80 + 7 = 387. Every algorithm for adding or subtracting large numbers is secretly expanded form in action.
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