How many pupils do you think there are in a really big school, all the children added together? Could it reach a thousand? Hands up with your best guess.

The interactive shows numbers built from place-value blocks across four columns: thousands, hundreds, tens and units. Look at how each column is filled, and keep an eye on any column that sits empty.

Let's build some numbers together on the mat. I'll call a four-digit number, one of you comes to the board and builds it, and the rest of us check each column out loud. Watch the thousands column carefully each time. We'll build 3,628 first, then the trickier 5,030.

Now we build these numbers together at the board: 3,012, then 5,600, then 7,083, then 9,009. The zeros catch people out, so before a pupil checks each one we'll all name the empty column out loud together first.

What we did today

• We built four-digit numbers using a thousands column.
• We traded ten hundreds for one thousand and saw the value stayed the same.
• We read numbers with zeros in the middle, naming the empty columns.

Coming up

Next we say four-digit numbers out loud, turning the digits into words and the words back into digits.