Fermat's little theorem and fake primes.

The mathematical problem with turbulence.

How crinkly is crinkly?

Count around the clock.

Capturing symmetry with algebra.

Why the humble average can be grossly misleading.

How to write a sum that's infinitely long.

Euclid's fourth axiom says that all right angles are equal. But isn't that obvious?

Five basic facts from the father of geometry.

The Indian way of adding fractions makes things easier (with musical explanation).