He studied "Fuzzy math" when he was a kid.
Michelle Malkin Fuzzy math: A nationwide epidemic
".....Across the country, from New York City to Seattle, parents are wising up to math fads like “Fuzzy Math.” Sounds harmless enough, right? It’s cleverly marketed as a “University of Chicago” program. Impressive! Right? But then you start to sense something’s not adding up when your kid starts second grade and comes home with the same kindergarten-level addition and subtraction problems — for the second year in a row......"