KS2

Adding 3-digit and 2-digit numbers

Part ofMathsAdding and subtractingYear 3

What is column addition?

Omi looking at a column addition calculation

Column addition is a way of adding numbers together.

It's helpful when you're adding two-digit or three-digit numbers together.

When you do column addition, you lay out the numbers you are adding above each other in columns. That's where the method gets its name from!

Omi looking at a column addition calculation

Activity: Adding 3-digit and 2-digit numbers

Complete this interactive activity to understand how to add numbers using column addition. Then put your knowledge to the test!

Using column addition

Let's look at how to solve the sum 237 + 25.

First, let's look at 237. This number has 2 hundreds, 3 tens and 7 ones.

A place value table showing the number 237 with 2 hundred counters, 3 tens counters and 7 ones counters.

The number 25 has 2 tens and 5 ones.

A place value table for the number 25 with no hundred counters, two tens counters and 5 ones counters.

Now let's write this out as a column addition to work out the answer.

You can use place value headings to help.

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Start with the column furthest to the right. In this sum, this is the ones column. 7 ones + 5 ones = 12 ones
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You need to group the ten into the tens column. We do this by marking it like this. Now you add the next column - the tens. 3 tens + 2 tens + 1 ten (from the regrouping) = 6 tens
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That is 60. You write 6 tens in the tens column like this. Finally, add the hundreds. 2 hundreds + 0 hundreds = 2 hundreds
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The answer is 262.

Always arrange your place value columns carefully.

Make sure that the ones are under the ones, the tens are under the tens and the hundreds are under the hundreds before you begin to add.

Example 1

What is 142 + 36?

Let's write it in a column addition grid.

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First you add the column on the right hand side. This is the ones column. 2 ones + 6 ones = 8 ones
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Write the 8 in the ones column.
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Now add the tens column. 4 tens + 3 tens = 7 tens
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Write the 7 in the tens column.
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Now add the hundreds column. 1 hundred + 0 hundreds = 1 hundred
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The answer is 178. 142 + 36 = 178.

Example 2

What is 234 + 57?

Let's write it in a column addition grid.

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First you add the column on the right hand side. This is the ones column. 4 ones + 7 ones = 11 ones
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We need to regroup the ten into the tens column by marking it and writing 1 in the ones column.
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Now add the tens column. 3 tens + 5 tens + 1 ten (from regrouping) = 9 tens
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Write the 9 in the tens column.
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Now add the hundreds column. 2 hundreds + 0 hundreds = 2 hundreds
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The answer is 291.

Example 3

What is 463 + 89?

Let's write it in a column addition grid.

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Image caption,
First you add the column on the right hand side. This is the ones column. 3 ones + 9 ones = 12 ones
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We need to regroup the ten into the tens column by marking it and write 2 in the ones column.
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Now add the tens column. 6 tens + 8 tens + 1 ten (from regrouping) = 15 tens 15 tens is 150.
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We need to regroup the hundred into the hundred column by marking it and add 5 in the tens column.
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Now add the hundreds column. 4 hundreds + 0 hundreds + 1 hundred (from regrouping) = 5 hundreds. Write the 5 in the hundreds column.
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The answer is 552.

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