These quizzes are about the basic adult things everyone should know, but school didn't bother to teach us. We may never know how to balance a checkbook, but at least we know the Pythagorean Theorem.

For over two millennia, mathematicians agreed on one thing: you can’t use trigonometry to prove Pythagoras’ Theorem—because trigonometry is built on it. That logic, drilled into students and scholars ...