## Thursday, November 10, 2016

### Day 54: Mental Math

I started new warm-ups this week and, as a result, am spending more time than normal getting the students used to them.

Today was "Think Through This Thursday."

When students arrived, they saw an expression on the board: 8*6

I told them that I purposely selected an easy problem because the answer wasn't important.  The point of this warm-up is to gt them to think about their mental strategies for solving problems.  Since this is the first time we did it, I got the answers I expected.

"I added 6 to itself 8 times."
Me: "Really?  When asked to do 8*6, you sat there and went '6, 12, 18, 24, 30, 36, 42, 48'? I find that hard to believe."

"I made a box that was 8 long and 6 tall and counted the boxes inside."
Me: "...riiiiiight."

"I used mental math" and "I just knew that 8*6 was 48."

So I started putting my methods on the board.

"For me, multiplying by 5 or 10 is much easier, so I would multiply 8 by 5 to get 40, then add in the last 8 to get 48."

This started the ideas flowing and soon the board was full or great methods, including several that I hadn't seen before.

I was very pleased with how well they took to this activity and I'm looking forward to next week, especially now that they have a solid idea of what we're doing.

In the pre-algebra class, we continued our discussion of transformations by having the kids develop their own tessellations.  They were very excited to be doing something creative and several had to restart because they didn't have a repeated pattern, or hadn't planned it well enough.  Overall, I was very proud of the work they were doing and we will continue it tomorrow.

I also had a formal observation today for the third time since 2006.  I'm very much looking forward to the feedback.

#### 1 comment:

1. This sounds awesome! My methods students are out doing number talks / mental maths with their students currently, and it's so wonderful to read in their post-lesson reflections about how students who are normally uninterested in math suddenly light up when people take genuine interest in their thinking, rather than in the answer. My favorite method for fostering this is similar to what you describe - giving kids the answer so that it's completely off the table. "So little do I care about you getting the right answer that I'll go ahead and just put it up here. So what work DO I want you to be doing in those brains of yours?"

Exciting stuff - I hope you are able to learn and grow from your observation.