What’s up? How do you help kids avoid this mistake?

Thanks again to Andy Zsiga for the submission.

  • You mean the mistake of inverting the slopes? Visualize! Draw a little graph! Then you’ll remember that the change in the Y-coordinate is the “rise”!

    For the mistakes in combining positive and negative numbers, relate it to money. -3 means your checking account is overdrawn 3 dollars. Minus 18 means you just did a debit card swipe for another 18 dollars. What’s your balance now? The analogy doesn’t work as well for subtracting a negative number, but it’s a start.

    • On the subtracting a negative number, you could relate it to forgiving a debt. If you overdrew by 21 dollars and then the banker had compassion and decided to forgive $10 of the debt, how much would you owe?

      • Oh, that’s good! They’re going to “take away” that -$10 liability.