New work on the problem of “scissors congruence” explains when it’s possible to slice up one shape and reassemble it as another. If you have two flat paper shapes and a pair of scissors, can you cut ...

When most people think of shapes, they imagine a triangle, a rectangle, or maybe even a fancier-sounding rhombus or trapezoid. But to mathematicians, shapes encompass a vast universe of surprising ...

Make 3-dimensional objects out of 2-dimensional shapes and use them to send secret messages! Ask, "What’s the difference between 2-dimensional and 3-dimensional objects? Where else do we see ...