Today during math class I was trying to explain to students why the problem h - (-19) = 130 (it was the equation from a math word problem) had to be re-written as h + 19 = 130. They were having a really hard time with it. I remember my math teachers saying, "If you'll just remember the rules you'll be fine (two negatives make a positive, etc.)". I was soooo tempted to tell them that, but I knew that there were several students who wanted to know the "why".
I had tried two examples with limited success. But majority of them still didn't understand why it should be switched to a positive. As I was sitting with a student one-on-one helping him understand why it had to be switched I had another idea. Here's how I explained it:
When I taught at __________ elementary I had a lot of these conversations with students. "Okay class, get out your pencils for math." "Um, Mrs. H? I don't got no pencil." "Okay, well get it out so and so." "Mrs. H, I just told you I don't have no pencil." "I know. Get it out." "Mrs. H, maybe you're not hearing me right. I said, I don't got not pencil." "Well, actually so and so what you're saying is you do have a pencil. Let's break it down. Your sentence can be written like this (I'd write it on the board.) Now what you're really saying is this: I do not have no pencil. So if you do not have no pencil you're saying you do have a pencil."
Now, my 6th graders picked up on this very quickly because they had just studied it in Reading/Language Arts. Each student came up with a sentence using a double negative. Once I was sure they understood the concept, I used it in the above equation and re-wrote it using language. So it read as follows:
h - (-19) = 130
h don't have no 19.
They got it! Later on, one of my kids who was totally into the whole thing said to me, "Mrs. H. That was a great illustration. I totally get it now. Did you think of that on your own?"
Yeah, your teacher does know a few things.
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