In the film Paddington in Peru, which opened this weekend, the plot revolves around a string bracelet that is said to contain mystical secrets.
The bracelet is supposed to be a ‘khipu’, which was the Incan way of recording numbers. Knots were made on string, and these pieces of string were attached together in a big bundle. The 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 asks you to repeat his decipherment (using an image of the same khipu he used, which is now in New York’s American Museum of Natural History).
Old rope
The image below is a section of a khipu laid out flat. The horizontal line is a cord on which all other strings are tied. Each vertical string is a three-digit number. Each set of four strings below the line is grouped together by a fifth string above the line. The ‘x’ and ‘o’ symbols represent two different types of knot.
Below is another set of four strings attached to the same horizontal cord. As in the previous diagram, the four strings under the cord are linked by a single one above, which I have left blank and marked with a ‘?’. What knots should go on this string?
To solve this problem, you need to look at the first image, work out the pattern, and then apply it to the second image.
I’ll be back at 5pm UK with the solution. Meanwhile NO SPOILERS – no movie plot spoilers, or puzzle spoilers. Please discuss Paddington, or Peru.
Today’s puzzle is extracted from my book The Language Lover’s Puzzle Book (2020), and originally appeared in the North American Computational Linguistics Olympiad.
My latest book is Think Twice: Solve the Puzzles That (Almost) Everyone Gets Wrong, which is a collection of counter-intuitive conundrums that make you think about thinking – while enjoying the pleasure of being misled. The questions are not ‘trick’ questions; instead, they reveal our biases and flawed reasoning.
Think Twice: Solve the Simple Puzzles (Almost) Everyone Gets Wrong. To support the Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply. (In the US, the book is called Puzzle Me Twice.)
I’ve been setting a puzzle here on alternate Mondays since 2015. I’m always on the look-out for great puzzles. If you would like to suggest one, email me.