Today’s puzzle is about defense. Now there is a word I have never used before in this column.
Less is more
Design an object that cannot go through an open window, but through one that is almost half closed.
Here are illustrations of a cross-section of the window that makes it clear what is required. The wall is blue, and the two wings are orange.
The problem seems ridiculous – how can something fit through the smaller hole but not the larger one? It seems to defy common sense!
Yet there is an object – or possibly several – that fits the bill. Can you imagine what that might look like?
And what if the left frame was completely closed, making it flush with the wall – can any objects that can’t go through the open window now go through?
I’ll be back at 5pm UK with the solution. Meanwhile NO SPOILERS. Book your favorite windows instead.
Source: QuanticA Russian mathematics magazine for school children.
In other hot news from the publishing world – my new book is out on Thursday! Think twice emerged from a puzzle I set last yearwhich was the most popular puzzle in the history of this column. This set me on a quest to find more counterintuitive puzzles—that is, questions that seem blindingly simple but catch us off guard. I have collected the best in this book.
Think Twice: Solve the Simple Riddles (Almost) Everyone Gets Wrong (Square Peg, ££12.99). To support the Guardian and Observer, order your copy from guardianbookshop.com. Delivery charges may apply.
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.
