Here is a number: 3,456. That is one way to write it. But hands up: is there more than one way we could break this same number up and still have exactly the same amount? What would you split off first?

The interactive shows each number built on the place-value mat. Look at how the blocks are piled in each example and keep an eye on whether the total actually changes.

We work through these four on the mat, one at a time. As each number appears, say its column values aloud with the class before we check it. The zeros are the ones that catch people out.

• Partition 4,050 into its columns.
• Build 4,700, then say how many hundreds it is.
• Partition 6,308 into its columns.
• Build 2,300, then say how many hundreds it is.

We work through these four numbers together, each a little trickier than the last. Two ask you to say how many hundreds the number is once you have built it, two are partition tasks, so check what each number is asking:

• Build 2,300, then say how many hundreds it is.
• Partition 4,050 into its columns.
• Build 6,800, then say how many hundreds it is.
• Partition 9,090 into its columns.

Predict where the blocks will land before we check each one.