Surely You're Joking, Mr. Feynman! Adventures of a Curious Character

by Richard P. Feynman

“Don’t you know how to square numbers near 50?” he says. “You square 50—that’s 2500—and subtract 100 times the difference of your number from 50 (in this case it’s 2), so you have 2300. If you want the correction, square the difference and add it on. That makes 2304.”