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H.2 Add two numbers up to four digits

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What is addition?

Addition is a mathematical operation that combines two or more numbers to find their total or sum.

Example:

When we add 3 apples and 2 apples together, we get 5 apples total.

3
+ 2
5
Note

Addition helps us find the total when we combine groups of items. The numbers we add are called addends, and the answer is called the sum.

Adding two digit numbers

When adding two-digit numbers, we add the ones place first, then the tens place.

Example:

Let's add 36 + 27 step by step:

36
+ 27
63

Step 1: Add the ones: 6 + 7 = 13. Write down 3 and carry over 1 to the tens place.

Step 2: Add the tens: 3 + 2 + 1 (carried over) = 6. Write down 6.

Step 3: The answer is 63.

Note

Always start adding from the rightmost column (ones place) and move left. If the sum in any column is 10 or more, carry over to the next column.

Adding three digit numbers

When adding three-digit numbers, we add ones first, then tens, then hundreds, carrying over when needed.

Example:

Let's add 478 + 253:

478
+ 253
731

Step 1: Add the ones: 8 + 3 = 11. Write down 1 and carry over 1 to the tens place.

Step 2: Add the tens: 7 + 5 + 1 (carried over) = 13. Write down 3 and carry over 1 to the hundreds place.

Step 3: Add the hundreds: 4 + 2 + 1 (carried over) = 7. Write down 7.

Step 4: The answer is 731.

Note

Always line up the numbers carefully by place value. Make sure ones are under ones, tens under tens, and hundreds under hundreds.

Adding four digit numbers

When adding four-digit numbers, we extend our method to include the thousands place after ones, tens, and hundreds.

Example:

Let's add 3,456 + 2,789:

3,456
+ 2,789
6,245

Step 1: Add the ones: 6 + 9 = 15. Write down 5 and carry over 1 to the tens place.

Step 2: Add the tens: 5 + 8 + 1 (carried over) = 14. Write down 4 and carry over 1 to the hundreds place.

Step 3: Add the hundreds: 4 + 7 + 1 (carried over) = 12. Write down 2 and carry over 1 to the thousands place.

Step 4: Add the thousands: 3 + 2 + 1 (carried over) = 6. Write down 6.

Step 5: The answer is 6,245.

Note

When working with larger numbers, it's helpful to use commas to separate thousands, hundreds, tens, and ones for easier reading.

Adding numbers with different place values

Sometimes we need to add numbers with different numbers of digits. We still line them up by place value.

Example:

Let's add 4,327 + 586:

4,327
+ 586
4,913

Step 1: Add the ones: 7 + 6 = 13. Write down 3 and carry over 1 to the tens place.

Step 2: Add the tens: 2 + 8 + 1 (carried over) = 11. Write down 1 and carry over 1 to the hundreds place.

Step 3: Add the hundreds: 3 + 5 + 1 (carried over) = 9. Write down 9.

Step 4: Bring down the 4 from the thousands place since there's nothing to add to it.

Step 5: The answer is 4,913.

Note

When one number has fewer digits, imagine there are zeros in the empty places. For example, 586 is the same as 0586.

Checking your work

It's important to check your addition to make sure you have the correct answer.

Example:

Let's check if 2,348 + 1,657 = 4,005 is correct:

2,348
+ 1,657
4,005

Method 1: Add the numbers again, being extra careful with carrying.

Method 2: Switch the order of the numbers and add again: 1,657 + 2,348 should also equal 4,005.

Method 3: Subtract one addend from the sum to see if you get the other addend: 4,005 - 2,348 should equal 1,657.

Note

Good mathematicians always check their work. If you have time, try using a different method to verify your answer.