Can You Solve My Problems? — Alex Bellos

You have a handful of coins spread out on the table in front of you. You put on a blindfold, and someone flips over some of the coins, then tells you how many are showing heads. You can now move the coins around and turn them over.

How can you separate the coins into two groups, so that each group has the same number of heads?

I picked up this book in a bookshop and read the above puzzle. I just couldn’t see how it could be possible. Intrigued, I bought the book. It’s packed full of clever, subtle, enlightening and fiendish puzzles.  Some of them I have been able to solve, some I gave up on, and some I am still grappling with.

Perhaps the cleverest and subtlest puzzle is Caliban’s Will, which was formulated in 1933 by Max Newman, who later worked at Bletchley Park deciphering German codes in the second world war. Bellos says, “I struggled with this one too, but that didn’t stop me marvelling at its sparseness, and whimpering at the brutal elegance of its solution.”

I read about Caliban’s Will and thought about the puzzle at great length, and finally came up with a solution. I was a bit uneasy about it though. And with good reason. At least the discussion of the solution specifically addressed my answer, and explained why it was wrong. As promised, the full solution is extremely austere and subtle; so much so that I still don’t fully understand it. But it makes me feel more clever just thinking about it. Bellos thinks this puzzle is work of genius. I agree.

This is a great book. I can feel my mind stretch as I read it.

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