Some magic math for the weekend

If you got some spare time on the weekend listen to Arthur Benjamin. He makes numbers dance. In his day job, he’s a professor
of math at Harvey Mudd College; in his other day job, he’s a
“Mathemagician,” taking the stage to perform high-speed
mental calculations, memorizations and other astounding math stunts.
It’s part of his drive to teach math and mental agility in interesting
ways.