Cool Information #28

Commutative Subtraction

Ever heard your math teacher say "Subtraction is not commutative! Only addition and multiplication is!" In case you don't know, commutative means you can switch things around. For example, 3+2=2+3 is true and so is 4×3=3×4. But subtraction is not commutative. For example, 3-2≠2-3 and 4-3≠3-4.

But, what's really weird is that subtraction is commutative in absolute value bars. [Absolute value is the distance a number is away from zero. (Absolute value is written with ||.)] For example, -3 is three numbers away from 0, so |-3|=3. Also, |3|=3 so |4-1|=3.] Going back, subtraction is commutative in absolute value bars! |2-4|=|4-2| |3-2|=|2-3| That is pretty cool!

-Me-