Two negative numbers…

Posted on January 18, 2016

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I actually had a student say that she had heard that “two negative numbers added make a postive number.”   Okay, it’s not the exact quote but she actually said “added,” instead of the more common “Two negatives make a positive.”

I told her (not my favorite response; need to work on this) “and that would always be wrong.”   I gave her the weight loss analogy (if I lose 3 pounds this week, and 4 pounds next week, have I gained weight?  … which I need to infuse with the words negative and positive…)

I told her about two negatives *multiplying* to make positive …   because multiplication is that much more powerful… and then said, “have you heard the saying that two wrongs don’t make a right?”  and encouraged her — when it was addition — to go to that when she was asking herself about “two negatives making a positive.”

Wish I knew if her affirming, confident responses were practiced, or legitimate.

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Posted in: math, Uncategorized