What number should be associated with the white box?

So a lot has happened since my last post! I left my job as a "lowly" mathematics aide and finally got a position as a full-time math teacher! It's been a crazy few months to say the least, but I'm very happy to say that I love the school I'm in. It's really brought back the creativity as a teacher.

One really cool thing that the school has turned me onto is "Number Talks" or "Math Talks". Popularized by Jo Boaler, it is the act of taking a small time out of class to look at a problem and try to figure it out using only mental math. No pencils, no paper, no air writing. Only the brain. Not only am I impressed with the level of mental math students can possess, but the interesting patterns they use to get to certain answers are astounding!

For example, I used the following picture as a Number Talk. The question posed was:
What number should be associated with the white box?

I tried to make the question as vague as possible to see what the students could come up with. And the answers were very interesting! The nice thing about it is that the students can't be wrong! As long as they come up with a good logical argument, it's a perfectly viable answer (Do I smell a CCSS Math Practice Standard?).

If you haven't tried these yet, it's definitely worth a shot! This page is riddled with ideas!

Until next time, happy math!

Robo