Puzzles

I like solving puzzles, it's fun and challenging and blah blah blah. Anyway, here are some of the more interesting ones that I've beaten my head against over the past short while. Stars are used to indicate difficulty: 0 (trivial), * (easy), ** (hard), and *** (very hard).

• A big bag of string - this one's great, lots of chances to be off-by-1 or off-by-k (*)
• Cabins and carpet - some riddles, if you know one you know how to get the rest (**)
• Chains - another easy one (0)
• Dinner at the Smith's - harder, but such a beautiful solution (**)
• Dropping eggs - I'm not sure why, but mathematicians seem to have it in for eggs (**)
• Horse racing and three other puzzles - for fans of horse racing (*)
• How heavy is the cannonball? - thanks to Alex Flint for this one, we concocted the variants in discussion over wine and dinner one evening (*)
• How old are my children? - a nice on from my time with BCG (*)
• Prison escape - not *** only because the solution is so embarrassingly simple, thanks to Alex Flint for this one (**)
• Sequence prediction - thanks to Nela Cicmil for this one, you will either find it extremely easy or absurdly hard (*)
• 60 Heads - more a statistics problem, ultimately a fascinating insight into how bad our statistical intuition really is (*)
• Three Litres - an easy one to start with (0)
• What colour is the bear? - like 'Dinner at the Smith's', but easier (*)