During the last year and a half, I have been working on my elementary math endorsement. As a result, my math instruction today looks nothing like it did years ago. Last year, I completely revamped how I taught double-digit addition (see it here), but I was stuck on how to improve my double-digit subtraction lessons. Then I stumbled across funny numbers, a math strategy developed by Greg Tang. I spent three days teaching my students how to make a funny number before I introduced double-digit subtraction with regrouping. OMG! On the very first day of instruction, I had multiple students that 'got it!' I heard students saying, "this is fun" and "this is really easy." I hope that by sharing what I did I can make your life a little bit easier when it comes to teaching double-digit subtraction, and reduce the amount of whining and frustration that you have to deal with when kids don't get it.
A funny number is basically a number that has been regrouped. It looks like this:
The first day that I introduced them, we worked with manipulatives. I showed them how to take one ten away from the tens, break it apart, and add it to the ones. The next two days, we worked with whiteboards. I would give them a number, and they would write the funny number. I made a screen for my Smartboard in Notebook that looked like this:
On the third day, I mixed it up a bit; I gave them the funny number, and they wrote the real number. In this case, the real number is 82.
Now when I teach, we cross out the top number, write the funny number above it, and breeze through the problem. All I can say is that Greg Tang is the best thing to happen to education since guided reading groups!
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