Hands up: how many fingers do you think there are in our whole class, if everyone holds up all ten? Could that number pass one hundred?

Now look at these three numbers. What is the same and what is different about them? 234, 305, 470.

The interactive shows numbers made from hundred-flats, ten-rods and units in the H, T and U columns. Look at each number and read the columns in turn. Keep an eye on any column that has nothing in it.

Let's build some numbers together. I'll call out a number, one of you builds it on our place-value mat in the hundreds, tens and units columns, and then we'll all read it back and check the columns are right. While one of you is at the board, the rest of us watch the mat and get ready to read the number aloud together.

Now let's build the very numbers you just wrote in your copy and check them on the board: 162, then 308, then 450, then 909. Before a pupil builds each one at the board, the whole class predicts the columns out loud. Then the pupil builds it and presses Check, and we all read it aloud. The zeros catch people out, so listen carefully for where each zero sits.

What we learned

• Ten tens make one hundred, so a new hundreds column opens on the left.
• A digit's value comes from the column it sits in, not the digit alone.
• A zero keeps a column empty but in place, so the other digits stay where they belong.

Coming up