THERE ARE plenty of puzzles involving a set of scales and objects of different weights. Here is one of the lesser known (invented by Paul Curry):

You have two red balls, two white balls and two black balls. Each pair comprises one ball slightly heavier than the other. The three heavier balls all weigh the same, as do the three lighter balls. Using a set of balance scales only twice, how can you determine which are the heavier and lighter of all three pairs?

(Answer tomorrow)

Yesterday's answers:

7 Deadly Sins

12 Labours of Hercules

84 Charing Cross Road