Two mathematicians have proved that a straightforward question—how hard is it to untie a knot?—has a complicated answer.

Two decades ago, the mathematician Moon Duchin spent her summers teaching geometry at Mathcamp, a program for mathematically talented teens. Campers contemplated notions such as how to prove whether a ...

Fix Excel formulas that won’t spill! Learn how to troubleshoot #VALUE errors caused by Analysis ToolPak functions and improve your workflow.

For centuries, humans have assumed that our thinking errors set us apart from the rest of the animal kingdom. From misjudging ...