How to Add a Three-Digit Number?

You can add three-digit numbers by using a place value work mat. The mat lists the place values: hundreds (H), tens (T), and ones. This method helps organize the numbers for addition.

Here's a more detailed breakdown:

1. Write the Numbers: Align the three-digit numbers vertically, ensuring the hundreds, tens, and ones digits are in their respective columns.

2. Add the Ones Column: Start by adding the digits in the ones column. If the sum is 10 or greater, carry over the tens digit to the tens column.

3. Add the Tens Column: Add the digits in the tens column, including any carry-over from the ones column. If the sum is 10 or greater, carry over the hundreds digit to the hundreds column.

4. Add the Hundreds Column: Add the digits in the hundreds column, including any carry-over from the tens column.

5. Write the Sum: Write down the sum in each column, from left to right (hundreds, tens, ones), to obtain the final answer.

Example:

Let's add 345 and 287.

Hundreds	Tens	Ones
3	4	5
2	8	7
---	---	---
		12 (5+7) -> Write down 2, carry-over 1 to the tens column
3	4+1	2
2	8
---	---	---
	13 (4+8+1) -> Write down 3, carry-over 1 to the hundreds column
3+1	3	2
2
---	---	---
6 (3+2+1)	3	2

Therefore, 345 + 287 = 632.

In summary, adding three-digit numbers involves aligning them according to place value, adding each column (ones, tens, hundreds) from right to left, and carrying over when the sum in a column is 10 or greater.