Somehow puzzles on weights and balances just never end! I found this great one in Martin Gardner’s The Colossal Book of Short Puzzles and Problems.
Five objects, no two the same weight, are to be ranked in order of increasing weight. You have available a balance scale but no weights. How can you rank the objects correctly in no more than seven separate weighings?
For two objects, of course, only one weighing is required. Three objects require three weighings.
For younger children, please do try the problem with four objects, where you are allowed no more than 5 weighings.
As always, please send your answers as comments within the blog (preferred), or send an e-mail to firstname.lastname@example.org. Please do share the puzzle with others if you like, and please also send puzzles that you have come across that you think I can share in this blog.