POTW: Freaky math

I just wrote about how staid companies do math (proven, verifiable, secure, quantitative stuff) and entrepreneurs and innovative companies create (unproven, to-be-tested) algorithms. Math's easy; crafting a new equation is difficult.

Thanks to Freakonomics, for the moment I stand corrected. Here's a slice of a freaky leap-day post:

A bat and a ball cost $1.10 in total. The bat costs $1.00 more than the ball. How much does the ball cost?

A. $1.10
B. $0.10
C. $0.05
D. $1.00
E. $0.15

Ten cents, I calculated.

Wrong. I turned to my horizontal-on-the-couch eight-year-old son. Without looking up from the Kings game, he blinked: That's easy dad. The ball costs five cents.