Column addition

Hello, and welcome to Myriora Maths! What is three hundred and forty-seven, plus two hundred and eighty-five? Big numbers are easier when we line them up in columns. Let's see how!

Why use columns? When numbers get big, it's hard to keep them all in your head. Columns keep the ones with the ones, the tens with the tens, and the hundreds with the hundreds. Then we only ever add small numbers.

First, write the numbers one above the other. Line up the ones on the right. Then the tens, then the hundreds. Draw a line underneath for the answer.

Always start with the ones. Seven plus five is twelve. Twelve is one ten and two ones. Write the two in the ones column. And carry the one ten over to the tens column, as a small one under the line.

Now the tens. Four plus eight is twelve, plus the one we carried makes thirteen. Write the three, and carry the one to the hundreds.

Now the hundreds. Three plus two is five, plus the one we carried makes six. So the answer is six hundred and thirty-two!

Why do we carry? Each column can only hold one digit, from zero to nine. Ten ones make one ten, so they move into the tens column. Ten tens make one hundred, so they move into the hundreds column. Nothing is lost: it just moves to the right place.

Let's try one together. What is one hundred and fifty-six, plus two hundred and thirty-eight? Here's a tip: start with the ones, then the tens, and finally the hundreds. Say the whole answer out loud!

Six plus eight is fourteen: write four, carry one. Five plus three, plus one, is nine. One plus two is three. The answer is three hundred and ninety-four! Well done if you said that!

Here's a question that catches lots of people. What is fifty-eight plus twenty-six? Some people write fourteen in the ones column, and get seven hundred and fourteen. But a column can only hold one digit! Write the four, and carry the one ten: eighty-four.

Your turn! What is four hundred and sixty-five, plus two hundred and seventy-eight? Pick the right card. You've got twenty seconds, or pause the video. Go!

Time's up! Five plus eight is thirteen: write three, carry one. Six plus seven, plus one, is fourteen: write four, carry one. Four plus two, plus one, is seven. It's seven hundred and forty-three!

Quick review. Line up the ones, tens and hundreds. Start with the ones, on the right. If a column makes ten or more, write the ones digit and carry the ten. See you next time!