Idea 6of 23Builds onTen of a place make one of the nextExpanded form shows each digit's value
Build a number more than one way
Can 42 315 be built without 4 ten thousands?
Today you'll discover
- how to trade a counter for ten
- why the number stays the same
- how to check a new build
Think first42 315 built with 4, 2, 3, 1 and 5 counters
Which of these also makes 42 315?
Decide first, then press Next. Check that the trade takes as well as gives.
A place-value mat with 4, 2, 3, 1 and 5 counters in the ten thousands, thousands, hundreds, tens and ones columns. One ten thousand counter fades and ten new counters appear in the thousands, making 3, 12, 3, 1 and 5. Two lines add both builds: 40 000 + 2 000 + 300 + 10 + 5 and 30 000 + 12 000 + 300 + 10 + 5, each 42 315. The last step shows 26 040.
See the whole ideathe big idea and the key word, in one place
The big idea
Trading 1 of a place for 10 of the next changes the build, not the number.
Easy to get wrongA trade both takes and gives. Take 1 ten thousand away and you must add 10 thousands, or the number changes.
For exampleA school orders 2 500 craft sticks: 25 boxes of 100, or 2 crates of 1 000 and 5 boxes of 100. Same sticks.
Key word
- decompose
- to break a number into parts that add up to it, in any way that works
Ready to use it?
- Show one number built two different ways.