Everybody's Go-To Methodical Mind

A student-aid guru, leaving behind the Web sites he built, moves to broaden his reach

Lisa DeJong for The Chronicle

Mr. Kantrowitz poses with his Peterbald cat Mimsy. In all of Pennsylvania, he boasts, he is one of only two people who breed the Russian hairless cats.
July 15, 2013 Premium content for subscribers. Subscribe Today

Mark Kantrowitz breeds hairless cats. He solves complicated math problems. He collects aboriginal art, folds elaborate origami, restores early battery-operated toys. And then there's the hobby that has turned into his career: knowing absolutely...

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