Base-ten blocks

Flats, rods and unit cubes you can drag on the projector: build a number, trade ten for one, break a rod into ones, and see the numeral the blocks make.

How to use it

Press + Hundred, + Ten or + One to add blocks (or press 3, 2 or 1). Drag a block to move it, or type a number under Build a number and press Build it.
To regroup, press 10 ones → 1 ten when there are ten ones on the stage. To go the other way, select a ten and press Break it apart.
Leave Show the number on to see the numeral and the expanded form, or switch it off and ask the class to say what number the blocks make.

Ideas for class

Build 36, then add 7 ones. Ask the class what they see: 43 has 4 tens and 3 ones, so ten of the ones must trade for a ten.
Subtract 18 from 52 by showing 52, then breaking a ten into ten ones so there are enough ones to take away 8.
Hide the numeral and make a number out of mixed blocks, such as 2 tens and 14 ones, and ask for the number. Then trade up and see the number does not change.
Build 124 and 142 with the same blocks in a different place value order. Ask which number is greater and how the blocks show it.
Make three hundreds, two tens and five ones, then take away one ten and ask how the number changed (it went down by ten).
Give pairs a number up to 999 and have them build it two ways: the fewest blocks, and with at least ten ones on the stage.
Show a number and ask students to write the expanded form on their whiteboards before you reveal it.

Questions

What are base-ten blocks?

A set of blocks that show place value: a small cube is one, a rod of ten cubes is ten, and a flat of ten rods is a hundred. Because a ten really is ten ones side by side, students can see why 10 ones can be traded for 1 ten.

How is this different from the real blocks?

Nothing breaks, nothing is lost, and every block appears where there is space. The tool also keeps count and writes the number and its expanded form, so you can check the arrangement against the numeral. Real blocks are still better for students who need to hold things, so use both.

How do I show regrouping in subtraction?

Build the top number. Select a ten and press Break it apart so there are enough ones, then select blocks and press Take away selected until the subtraction is done. The numeral at the side shows what is left.

What is the biggest number I can build?

Up to 999 with the Build it box, and as many blocks as fit on the stage (240) by hand. A thousand cube is not included because three-digit numbers are what most standards ask students to show with blocks.

Can I save a setup for tomorrow?

The blocks on the stage are remembered in this browser, and Share copies a link that starts with the same numbers of hundreds, tens and ones, which a colleague can open. The link keeps the counts, not where each block was placed.

Does it work with touch?

Yes. Drag with a finger, and the blocks are large enough to hit on a smart board. The arrow keys also move the selected block.

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Using base-ten blocks in class

Blocks make place value visible. Students who can only recite “tens and ones” often cannot say why 10 ones are the same as 1 ten, and blocks answer that question without a lecture. Spend more time on trading than on building: the trade is the idea.

Start with building and saying a number aloud (“three hundreds, two tens, four ones”).
Move to comparing: which has more, and how do you know?
Then adding and subtracting, where trades appear naturally when there are too many or too few ones.
Finish by dropping the blocks: draw them, then use only numerals.

Common mistakes

Counting a rod as one, not ten. Ask students to count its squares.
Reading 205 as “two hundred and fifty” because the ten blocks are missing. Show the empty tens place.
Trading but forgetting the count: always read the numeral before and after a trade; it must match.