Lesson Plan - Get It!
The sum of 247 and 59 is 306. What is the difference? Hmmm . . . that's different. How do you find the sum and difference of a 3-digit number?
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?
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:
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!
Second, add the numbers in the tens column.
Third, add the numbers in the hundreds column.
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!
Second, subtract the numbers in the tens column.
1 13 17
Third, subtract the number in the hundreds column.
1 13 17
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.