Arithmetic for middle school entrance exams. Even when the answer is correct on cram school tests or homework, when you ask, ...

Everyone knows that arithmetic is true: 2 + 2 = 4. But surprisingly, we don’t know why it’s true. By stepping outside the box of our usual way of thinking about numbers, my colleagues and I have ...

Everyone knows that 2 + 2 = 4, but why do we have arithmetic in the first place, and why is it true? Researchers at the University of Canterbury have recently answered these questions by "reverse ...

Consider this sequence of numbers: 5, 7, 9. Can you spot the pattern? Here’s another with the same pattern: 15, 19, 23. One more: 232, 235, 238. “Three equally spaced things,” says Raghu Meka, a ...

Everyone knows that arithmetic is true: 2 + 2 = 4. But surprisingly, we don't know why it's true. By stepping outside the box of our usual way of thinking about numbers, my colleagues and I have ...