12 rubies weighing problem/riddle
i searched for this one if it is posted before, apparently not, but if it is, sorry for that.
a merchant has 12 identical rubies with equal masses that he wants to put on display, however, he knows that one of these rubies is special in the sense that its either heavier or lighter than the rest. he wants to know which one of them is the special one AND if it is heavier or lighter. however, he has a balance scale that he can use only 3 times. how would he identify the special ruby and know if its heavier or lighter.
the scale can only tell which side is heavier, the merchant cant measure the angle at which its sloped.
the rubies are of identical shapes, but they can be labeled.
the merchant doesnt have any other tools but the balance scale.