# Maths in a minute

Want facts and want them fast? Our *Maths in a minute* series explores key mathematical concepts in just a few words. From symmetry to Euclid's axioms, and from binary numbers to the prosecutor's fallacy, learn some maths without too much effort.

Maths in a minute: Euclid's fourth axiom

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

Maths in a minute: Adding fractions (the easy way)

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

Maths in a minute: Watch your units!

How to lose a spacecraft in the most embarrassing way possible.