- 01 Feb '05 15:52apologies if this has appeared before

you have eight balls, they all look and feel identical. however one of them weighs slightly less than the others (you can't tell by holding them).

you want to work out which is the lighter ball.

all you have is a pair of ballancing scales (ie tells you if stuff on one side weighs the same as stuff on the other side).

you can fit as many balls as you like on the scales.

how can you find out for sure (ie not relying on luck) the identity of the lighter ball IN THE LEAST NUMBER OF WEIGHINGS? - 01 Feb '05 16:33

Indeed it has. In fact, I was thinking of compiling a 'Posers & Puzzles FAQ' section on my website, including a general approach to the balance problem. In this case, the answer is that 2 weighings are needed, but I'll leave others to explain why.*Originally posted by murrow***apologies if this has appeared before**