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 ...

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 ...

Playing with arithmetic can lead us to unexpected and profound discoveries that point toward deeper mathematics and sometimes even deeper science. We solved our last Insights puzzle by performing some ...

In the early years of the Republic, arithmetic was generally taught to teenaged boys planning careers in commerce, often by private tutors. With the advent of free common or elementary schools ...

Barbie caught a lot of flack back in the ’90s for declaring, “Math class is tough!” Today we find ourselves in the disorienting position of defending her. We recently got a note from an anonymous ...

On his website andertoons.com, illustrator Mark Anderson has a cartoon in which a boy is handing his teacher an assignment. “To show how well I understand fractions,” he says, “I only did half of my ...