Teaching area of complex shapes

Today I saw the movie, The Martian. Unbelievable.

I had read the book. I knew it was going to be good. But I don’t think I’ve ever been on such a math high before! If you are a math teacher, you are probably among the people in this world who can understand how completely amazing it is to see Math Damon, huge on the big screen, saying (something like), “You’re going to die. You can die or you can do the math. Just solve one problem and then solve the next one. Do the math.” I think he said, “Just do the math” like 6 times in that movie! So great! I think we may start having a Martian math problem of the week….

I’m getting ready to correct my quizzes for last week. I always correct quizzes over the weekend. Probably sounds sort of appalling to many people but it’s kind of my thing. I don’t grade homework and I feel like if I don’t get their Friday assessments back to them quickly, then we really lose momentum. Today, I kind of know what I’m going to see. And, frankly, even though it’s unrealistic, anything less than 100% meeting or exceeding standard is always disappointing. I know they can do it. We just can’t always get there on the quiz or test. So then I have to figure out what’s next.

We are working on 6.G.1, 2 and 4….composing and deconstructing complex shapes to find area, surface area and volume. These usually seem to be tricky for a lot of kids to master and the ideas are certainly challenging to teach, at least in an interesting way. This time we really got hands-on with pattern blocks and actually physically building shapes before calculating their area. I thought it was helping but only about 50% of my 90 or so 6th graders met standard. So I kept trying to hit it last week, really emphasizing that surface area IS composing. But, of course, still not 100% yet. And worse, really, is the kids who do crazy weird stuff like adding up all the side lengths. And I do mean ALL of them. Or, my personal not-favorite:  multiplying ALL the side lengths so that the surface area of a 3x4x2 prism comes out to hundreds or somehow thousands…. We need to move on to our next unit, which is algebra. It will be a relief to get a break from fractions and decimals, as the 6th grade algebra standards focus on whole numbers, for the most part. But, I’ll have lots of kids to keep working with after school. I’m going to try getting the blocks back out and see what that does. We use Khan Academy, too, so we’ll try that as well. And my partner in crime and I will keep thinking about how we could do this better next time. He hates nets. Don’t actually get him started on that topic…

In the meantime, I also started thinking about how we assess. Does it necessarily have to be a traditional math quiz? I’m going to give the kids 10 or 15 minutes tomorrow to just tell me about how they would solve a problem. And, of course, since I’m all “Martian-ed out” I’ll throw something from the Martian on there. Like… “The Martian is an amazing math and science movie. In the movie Mark Watney is stranded on Mars and has to grow potatoes. He needs to cover the floor of his living space with dirt. What math would you do to figure out how much dirt he needs?” And then I created a shape using a rectangle, a square and a hexagon. It will be fun to see what they can say and do. No numbers. Just shapes and tell me.


We’ll see what happens.

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