Steven Strogatz, an applied math prof at Cornell, has started a series on the NYT site to re-teach basic math from an adult perspective, with the goal to show "why it's so enthralling."

I love the second installment, which explores the way that using rocks in place of digits (i.e., six rocks rather than the number "6″) can provide unexpected insight on seemingly tough problems:

For example, instead of adding just two odd numbers together, suppose we add all the consecutive odd numbers...