February 26, 2024

For the first time in eight years that mysteries have been posted on alternate Mondays, today’s publication date coincides with Christmas Day. Festive greetings everyone!

What numerical gifts did Santa bring this year? For North Americans, there’s a glorious date next week: it’s New Year’s Eve 123123.

Let us now turn our thoughts to 24, the number of the coming year.

Puzzle 1 Can you make 24 using only the numbers 1 to 9 and the basic arithmetic operations? Here is one way that puts all the numbers in the right order.

(123456 x 7) + 8 + 9

Beginner level: find another way.

Advanced level: find another way with the numbers in vice versa order

[By basic arithmetical operations I mean +, –, x, ÷, exponent, brackets, and concatenation, i.e. when you run numbers together as in ‘23456’ above. If you get stuck, as a gesture of festive goodwill, I will also allow square roots and decimal points.]

Broke it

Speaking of numbers, I’d like to thank the readers of this column for making this year its most successful ever. In 2023, the column received more than 5.3 million page views – a 36 percent increase over 2022. Way to go, mysteries!

The most popular column of this year was by far Almost everyone gets the simple question wrong, which contains a task invented a century ago to test children’s IQs. (The background of the puzzle is as heartwarming as any Christmas story.)

Since I thought you might like this problem, I asked Jane Braybrook, who rediscovered the puzzle when looking for ways to help her disabled son with his cognitive development, to produce some new examples. Here they are:

Puzzle 2 In each of the examples below, the shapes A to L are either color blocks or stencils (ie squares with holes in them.) The shape on top is made by stacking A to L on top of each other. Your task is to work out which stencils/squares are used and in which order.

xmas puzzle 1 stenciletto
Illustration: Stenciletto
xmas puzzle 2 stenciletto
Illustration: Stenciletto
xmas puzzle 3 stenciletto
Illustration: Stenciletto
xmas puzzle 4 stenciletto
Illustration: Stenciletto
xmas puzzle 5 stenciletto
Illustration: Stenciletto

PLEASE NO SPOILERS. Please discuss your favorite facts about the number 24 instead.

I’ll be back at 5pm UK with solutions

Thanks to Inder Taneja, who every Christmas compiles an entire document of incredible numbers of facts about the coming year, including the example above. His website is a plethora of numerical curiosities.

Thanks to Jane Braybrook for the stencil puzzles. You can find more of them on her app Stenciletto, which can be downloaded www.smileyworldgames.com.

Finally, I’m still pinching myself that I was asked to represent my alma mater, Corpus Christi College, Oxford, at this year’s Christmas University Challenge. It was a dream come true. Fingers on buzzers! Appetizer for ten! Last week we won our first round battle against the University of Edinburgh. We appear in the semi-final on Wednesday, 20:30 on BBC2. Wish us luck!

Corpus Christi v Edinburgh Christmas University Challenge Alex Bellos Steve Waters Michael Cockerell Francesca Happé
Team Corps: Psychology professor Francesca Happé, documentary producer Michael Cockerell, myself, playwright Steve Waters. (And a pelican mascot sits on the snow.) Photo: BBC

I’ve been doing a puzzle here on alternate Mondays since 2015. I’m always on the lookout for great puzzles. If you want to suggest one, email me.

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