A. Alcuni esercizi svolti

Described image figs/nerd_sniping.png

[[Hat Guy is sitting on a chair, the Normal Guy is standing next to him. Across the street another man is coming from a building.]] Hat Guy: There's a certain type of brain that's easily disabled. If you show it an interesting problem, it involuntarily drops everything else to work on it. [[The man across the street is about to enter a crosswalk]] Hat Guy: This has led me to invent a new sport: nerd sniping. See that physicist crossing the road? [[Hat Guy holds up a sign]] Hat Guy: HEY! [[There is an image of a grid with resistors on every connection, two nodes a knight's move apart are marked with red circles.]] The sign reads: On this infinite grid of ideal one-ohm resistors, what's the equivalent resistance between the two marked nodes? Physicist on the street: It's... Hmm. Interesting. Maybe if you start with... No. Wait. Hmm... You could-- [[A truck is zooming past, apparently where the physicist just stood]] <<FOOOOM>> Normal guy: I will have not part in this. Hat Guy: C'mon, make a sign. It's fun! Physicists are two points, mathematicians three. {{Alt: I first saw this problem on the Google Labs Aptitude Test. A professor and I filled a blackboard without getting anywhere. Have fun.}}

[http://xkcd.com/356/]