In a classroom in south-east Mexico, eight-year-old Verónica Yuritzi Martín Puc’s hand shoots up with the answer. On her desk is a sheet of paper with a simple grid drawn on it. She has put two dried black beans in one of the squares on her grid and a shell of dried pasta in another. More beans, pasta and some thin wooden blocks lie unused in piles on the desk.
Yuri, as she is known, is learning maths — but not the way most children do. Instead, she is following a method invented thousands of years ago by her Maya ancestors.