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Add two three-digit numbers

In this worksheet, students add together two-digit numbers by adding the units, then adding the tens and combining the results.

Worksheet Overview

In this activity, we will learn how to add together two three-digit numbers.


Three-digit numbers have hundreds, tens and ones. 

One way to add them together is to partition them into their place value.

453 + 429

453 has four hundreds, five tens, and three ones. 

429 has four hundreds, two tens, and nine ones. 


Once partitioned, we can add the hundreds, tens and ones.

3 + 9 = 12

50 + 20 = 70

400 + 400 = 800


Lastly, we can add together these numbers to find out the total sum.

800 + 70 + 12 = 882


Let's try an example together.



Add the numbers:

628 + 257



First we add the ones: 8 + 7 = 15

Then we add the tens: 20 + 50 = 70

Then we add the hundreds: 600 + 200 = 800

Lastly, we combine the three results: 800 + 70 + 15 = 885

The answer is 885


Now it's your turn to try some questions like this. 

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