Bad thing for a moderator to say, perhaps, but I think this puzzle is worth looking at,
even if it may have been posted before. So if you happen to know the answer from
a previous posting, let it ride for a few days.
There are three pairs of balls - red, white, and blue.
In each pair one ball is a little bit heavier than another one.
All the heavy balls weigh the same, and all the light balls weigh the same.
Also you have a balance scale with exactly three outcomes: <, = and >.
You need to identify the three heavy balls.
How many times do you need to use the scale?