3-Digit Addition and Subtraction

Lesson Plan - Get It!

Audio:

The sum is the answer you get when you add two numbers.

When you subtract two numbers, your answer is the difference.

What is the sum of 5 and 5, or 5 + 5?

• Right! The sum is 10.

What is the difference between 10 and 5, or 10 - 5?

• Right again! The difference is 5.

You know how to add and subtract 1-digit and 2-digit numbers. Now you will learn how to find the sum and difference of 3-digit numbers!

To begin, you need to line up the numbers in the correct place value:

So, 247 + 59 would look like this:

    247

   + 59

You must place the ones, tens, and hundreds in the right place to get the right answer!

So, what’s the difference between adding and subtracting 3-digit numbers?

To add 3-digit numbers:

First, add the numbers in the ones column. Don't forget to regroup!

      ₁

   247

 +  59

       6

Second, add the numbers in the tens column.

    _{1 1}

   247

 +  59

     06

Third, add the numbers in the hundreds column.

   _{1 1}

   247

+   59

   306

The sum of 247 and 59 is 306.

To subtract 3-digit numbers:

First, subtract the numbers in the ones column. Don't forget to regroup!

    _{3 17}

  247

-   59

      8

Second, subtract the numbers in the tens column.

   _{1 13 17}

   247

-   59

    88

Third, subtract the number in the hundreds column.

  _{1 13 17}

  247

-   59

  188

The difference of 247 and 59 is 188.

So you see, it really is as simple as 1-2-3! Tell a parent or teacher how you can add or subtract 3-digit numbers in three easy steps.

Now it’s your turn to try a few practice problems. Check your understanding in the Got It? section.