## Halloween math

The girls both wore their Halloween costumes to the lesson this week, and they insisted that the lesson had to be scary.  The only thing that came to mind was to turn off the lights and start telling stories of numbers eating each other, while asking the girls some mental math questions.  However, the girls were so distracted by each others squealing and screams of “this is not scary” that they were messing up even basic additions.  I knew that I had to turn the lights back on and distract them with something quickly.  Colorful beads seemed to be just the thing.

I decided to have them play a bit with divisibility.  I would say a number and they’d have to tell me whether they could make that number using just the 1’s, just the 2’s, just the 3’s, etc.  To make it simple, I started out with 4.  They were immediately able to tell me that they could make it out of 1’s and 2’s.  It took them a moment longer to decide about 3’s and 4’s, but they answered correctly without much trouble.  When I asked them why one can’t make 4 out of just 3’s the reply was, “because 6 is more than 4!”  Who can argue with that?