Pi is undoubtedly the world's most popular irrational number. And that's because it's unequivocally cool — I mean, what other mathematical constant has its own day? On its face, pi is a simple concept ...

If Levi Vaughan, a 5-year-old kindergartner in Braidwood, Ill., makes it through math class without a meltdown, it’s a good day. The transition to school has been tough in other ways for Levi, said ...