Building Big Numbers: Take Two!

As Willow moves into multiplication, Sydney is moving into multi-digit addition, and thus I find myself, almost exactly one year to the date that I last wrote about this activity, again writing about building big numbers, Montessori-style.

Building big numbers, an activity so successful and so enjoyed, has evolved a little since that first mention. Now, instead of stating a number to be built, I have Sydney first lay out each grouping of Base Ten cards--the thousands in one stack, the hundreds in another, the tens in a third, and the units at the last. She lays out each stack so that it's in the correct sequence, with the thousand stack all the way to the left and the unit stack all the way to the right.

The cards aren't sequenced in order within each stack, so that next, when Sydney chooses the top card from each stack, she has a completely random number. She lays each card out in correct Base Ten order on the rug, then builds that number with the Base Ten blocks:


When the number is built, Sydney writes the number down (if she gets stuck, remember that she can stack the Base Ten number cards, thousands on the bottom to units on the top, to see the correct number), then uses our Base Ten block stamps to record how it was built:

It's not uncommon, of course, for her to stop in the middle of building a number to build, well, something else:

That's what Syd's doing right now, in fact--building and recording big numbers while Will reviews multi-digit addition using workbook pages (Yes, I still have a fever today, and a cough, and a runny nose, and a feeling of general lousiness, and yes, I do regret not getting a flu shot--this illness has been miserable!). I had to stop writing just a second ago and go over to the rug, because Sydney said to me, conversationally, "Forty tens make 40!"

"Oops!" I thought. When I sat down with her, however, I saw that Syd had really just mixed up her wording--when the kids are making big discoveries or otherwise thinking hard, their grammar, vocabulary, and handwriting all regress, because their brains are busy elsewhere. What she was doing was comparing the tiny unit to the ten bar and again noticing that each ten bar measured exactly ten units. She already knows this, of course, but something else was clearly going on in her head that turned this familiar concept brand-new. And when I reminded her that this one is one unit and this one is a ten bar, she immediately said, "Forty UNITS make 40!"

So now off I go to see how much of a thousand cube we can build with all the units that we have on hand.