The answer to today’s Inca-nundrum

Earlier today I set you a puzzle about a ‘khipu’, the Incan method of recording numbers with knots on string that features in Paddington in Peru. Here it is again with the answer.

Incans used khipus to record dates, taxes and measurements, among other things. Knowledge of how khipus represented numbers was lost after the Spanish conquest, until a high school maths teacher in Brooklyn worked it out in 1912. Today’s puzzle asked you you to repeat his decipherment.