When numbers get bigger than a single digit, adding them in your head gets hard. There is a tidy way to do it on paper: write the numbers stacked on top of each other, lined up by place value — ones under ones, tens under tens — and add one column at a time. This is column addition, and it is just ordinary addition done one place at a time.

Line the numbers up on the right, draw a line underneath, and you are ready to add:

Now add the ones column first. Here the ones are 7 and 5, and 7 + 5 = 12. But a column can only hold a single digit! Twelve is one ten and two ones, so we write the 2 in the ones place and carry the 1 ten over to the top of the tens column. Carrying is just the bundling idea from place value: ten ones become one ten, and that ten joins the next column.

Then add the tens column, remembering the carried ten: 1 + 2 + 3 = 6 tens. Write the 6, and the total is 62:

See it built

Watch the sum come together one column at a time. First the numbers stack up; then the ones are added and the ten is carried; then the tens; then the total. Step through it.

See it explained

Sal Khan adds two numbers with regrouping — exactly the carrying we just did.