July 22, 2024

Nice thinking is the title of my new book (published on September 5) and it is also my advice for today’s puzzles.

1. Hello ducklings

There are two ducks in front of two ducks, two ducks behind two ducks and two ducks in between. What is the minimum number of ducks?

2. Concentric puzzle

Imagine I’m walking around a circle whose center is Big Ben. For the purposes of this question, assume I can walk on water.

When the radius is 1 km, I will walk approximately 6.28 km

When the radius is 100 km, I will walk approximately 628 km

When the radius is 10,000 km, I will walk about 62,800 km?

(The circumference of a circle is twice the radius times pi, which is 3.14 to two decimal places.)

3. Hanging from a rope

A bottle of water hangs from the ceiling by a rope. A handle hangs from the bottle by a piece of the same type of rope, as shown below.

You pull the handle off. A string breaks. Which one?

a) the top one

b) the bottom one

c) they break at the same time

In each of these three questions, the obvious answer is not the right one. (Or maybe it is, I can double bluff.)

I hope you get them all wrong, of course. For a start, I have the headline to live up to. (Though TBF, when I was the only reader of this column, it was true.) Are you up to the challenge?

I’ll be back at 5pm UK with the answers. Meanwhile NO SPOILERS. Please reserve ducks.

Puzzles that look very simple but surprise us are – I think – the most fun kind of puzzle, and I’ve put in 70 of my favorite examples. Nice thinking. (Excluding today’s.) There’s something irresistible about a puzzle that subtly tricks us, or that reveals something unexpected about the world.

The book isn’t out until September 5, but you can already pre-order. If you’re tempted, please, ahem, do not think well Pre-orders really help give a book momentum. Help it the Murder from 2024!

Think twice: Solve the simple puzzles (almost) everyone gets wrong by Alex Bellos (Square Peg, £12.99). To support the Guardian and Observer, order your copy from guardianbookshop.com. Delivery charges may apply.

Thanks to Fabio Ciuffoli, who first told me about the ducks, and Nikolai Andreev, who told me about the circles.

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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