Ana Darcy Méndez is very, very good at math. She had to be, to navigate a vessel 25 light years from Thomo to Earth! Her son Julio is even better. Both were fascinated by this marvelous card trick:
Notice that the person performing it begs someone for an explanation. We can offer that gentleman an explanation, since Ana and Julio, her son, spent the better part of an hour playing with it. Ana said it's basically a simple matter of "odds and evens," made more confusing by all the cutting of the cards, which leaves their basic order unchanged.
Math teachers are always asking their students to "Show your work." In case you'd like to see Ana's and Julio's work, here it is, in Ana's handwriting.
If you've read Ana's stories, you'll already know the fun her family has with puzzles and other games. Just imagine them talking this through and jotting down the results. They love this kind of thing!
(Right click to another tab to enlarge.)
Other Méndez family games and puzzles: