What is column addition?
Column addition is the most orderly way to add numbers with two or more digits. Instead of trying to keep everything in their head, the child writes the numbers one below the other and works one column at a time: ones, tens, hundreds.
This method is important in primary school because it turns one big calculation into many small ones. The tricky part is carrying: when a column adds up to more than 9, part of the result has to move to the next column.
The mechanism: ones with ones, tens with tens
The basic rule is simple: every digit goes in the right column. Ones sit under ones, tens under tens, hundreds under hundreds. And you always start from the right.
Stack them properly
Write the numbers right-aligned. If the bottom number has fewer digits, leave the missing column on the left blank.
Start from the ones
Don't start from the tens. In column operations you work from right to left.
Handle the carry
If the column sum is 10 or more, write the ones digit and carry the ten over to the next column.
Worked example: 47 + 38
- Stack the numbers with the ones below the ones and the tens below the tens.
- Add the ones: 7 + 8 = 15. Write 5 and carry 1 above the tens.
- Add the tens + carry: 4 + 3 + 1 = 8.
- Result: 47 + 38 = 85.
Why does 7 + 8 become 15?
15 contains 5 ones and 1 ten. The 5 stays in the ones column; the 1 is carried over to the tens column. Then the tens become 4 + 3 + 1.
This little split is the heart of carrying: nothing gets erased, the ten just moves to the right place.
Tip: when you explain carrying to a child, don't just say "put the 1 above". Tell them what's happening: 15 means 5 ones and 1 ten. That way carrying doesn't feel like a mysterious rule.
When do you need to carry?
You need to carry every time a column adds up to at least 10. It doesn't matter whether you're adding ones, tens or hundreds: the logic is always the same.
8 + 6 = 14: write 4 in the column and carry 1 to the next.
9 + 7 + 1 = 17: the +1 is a previous carry. Write 7 and carry 1.
5 + 4 = 9: no carry needed, the sum stays under 10.
The most common mistakes in column addition
Many children know how to add, but they make mistakes because they skip a step in the procedure. Here are the typical mistakes to watch out for.
Forgetting the carry
The child calculates 7 + 8 = 15, writes 5, but then forgets to add the 1 to the tens.
Misaligning the digits
If the ones end up under the tens, even a simple sum produces the wrong answer.
Starting from the left
In column addition you start from the right, because the carry from the ones can change the tens.
Confusing carry and result
In 15 the 5 goes below, while the 1 goes above the next column. They are two parts of the same number.
How Matematt helps the child overcome the problem
The problem with addition with carrying isn't just "doing the sum". It's remembering the order of the steps, knowing where to put each digit and not losing the carry. Matematt works precisely on this: it makes the procedure visible.
One step at a time
The app doesn't ask for the final result straight away: it guides the child column by column, just like a teacher at the blackboard.
Carries highlighted
The carry is clearly shown, so it doesn't stay as an invisible mental step the child has to remember alone.
Contextual hints
The help text changes depending on which part of the exercise the child is on: ones first, then carry, then tens.
Mistakes as opportunities
If the child makes a mistake, the app brings them back to the right step instead of just marking the answer as wrong.
Column addition practice problems
Before moving on to big numbers, it's worth alternating exercises without carrying and exercises with carrying. That way the child understands when carrying really matters.
No carry
23 + 14
Ones below 10: practice for getting the alignment right.Carry in the ones
47 + 38
7 + 8 goes over 9: a carry to the tens appears.Carry in the tens
68 + 57
After the ones, the tens can also generate a new carry.Three digits
176 + 248
Same method, one extra column: ones, tens, hundreds.Frequently asked questions about column addition
How do you explain column addition to a child?
It helps to start from the value of the digits: ones, tens and hundreds. Then show that each column is added separately, always starting from the right.
What is carrying?
Carrying is the ten that moves to the next column when the sum of a column is more than 9. For example, 7 + 8 = 15: the 5 stays in the ones, the 1 moves to the tens.
Why does my child know how to add but get column addition wrong?
It's probably not a problem of addition, but of procedure: alignment, column order or handling the carry. That's why working step by step helps.
Does Matematt just give the answer or does it explain the steps too?
Matematt shows the steps: it points to the column to work on, highlights the carry and walks the child all the way to the final answer.