# ZeroSum Ruler (home)

## Blogging on math education and other related things

### Income and Debt with ZeroSum RulerJuly 10, 2011

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One of the ZeroSum ruler’s main purposes is to calculate debt/income problems.   In the problem “I owe you \$12 and pay you back just \$7. How much do I still owe you?” how do you come to your answer?   Do you count backwards from \$12 to \$7?   Or do you count forwards from \$7 to \$12?   No really, how much do I owe you?   How did you figure this out?    The ZeroSum ruler allows the student to count forwards instead of backwards just like we do in real life!    So why do we make our kids count backwards in school?

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### I can read your mind! (well, Algebra can :)January 9, 2011

If you have a good handle on your Algebra, you can read anyone’s mind!  This video (click the red triangle to go to the YouTube video) is just one case where I can read your mind straight through the computer! It’s true!   Can you develop an algebra trick that reads your friend’s mind? I bet you can!

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