Pubs are for drinking, socialising – and doing puzzles. Or so claims Headscratchers, a new compendium of puzzles from New Scientist magazine, from which today’s cranium-ticklers are taken. The first is a classic pub puzzle. (An inn-igma? a bam-booze-ler? A conun-dram?) Which is to say, it is a mathematical challenge that lends itself to being tackled in a group, and may lead to heated debate! 1. Creative addition The numbers 1 to 9 have been written on cards and left on a table. The left hand column adds to 21; the right to 24. Move a single card so that the two columns add to the same total. There’s a classic “aha” solution. Yet when this appeared in New Scientist, readers came up with at least ten more solutions. The level of lateral thinking tolerated may depend on personal taste, or on how many pints you have consumed. 2. The book of numbers Polly is writing a book containing the whole numbers from zero to infinity in alphabetical order. The first entry is ‘eight’. What number is second in the list? What number is second-last in the list? Note: above ‘one quadrillion’ (1015), there are no new number words. Instead, Polly strings numbers together, ie. 1018 is ‘one thousand quadrillion’ 3. Sick sweeks Which number is bigger? The product of all the numbers from 1 to 10 (meaning 1 x 2 x 3 x…x 9 x 10, and usually written 10!) or the number of seconds in six weeks? You are not allowed to solve this one using a calculator! I’ll be back with solutions and a discussion at 5pm UK. Please NO SPOILERS. Instead discuss your favourite pub puzzles and games. Today’s puzzles all come from Headscratchers: The Puzzle Book by Rob Eastaway and Brian Hobbs. Rob curates the New Scientist’s weekly puzzle and the puzzles in the book are taken from its pages. It’s a fantastic and varied collection of problems authored by some of the best puzzle setters around. UPDATE: To read the solutions click here. I set a puzzle here every two weeks on a Monday. I’m always on the look-out for great puzzles. If you would like to suggest one, email me. I am also the author, together with Ben Lyttleton, of the book series Football School, which explains the world through football. The Football School Encyclopaedia, our first full colour hardback, is out this week! Looking for a gift for a football fan aged 7 or up? It’s an open goal…