Zequals and Estimation

Alex Bellos discusses how the Incans used knots in string (Quipu) to record numbers.Check out Brilliant (get 20% off their premium service): https://brillian...

Rob Eastaway on his "zequals" estimation method - ruthless rounding!

The book is at http://amzn.to/Uf5mqv & extra footage at http://youtu.be/ND9NKCopbu0