You have six balls - three red and three black. All the red balls weigh differently, i.e. one of them is heavy, the other medium, and the third light. Each red ball has a black twin of the same weight. A heavy and a light ball put together weigh as much as two medium balls.
What is the least number of weighings required on a balancing scale to determine which is which?
(In reply to needs checking
by ant simmons)
but liars can figure ......
It must be wrong, since your way provides 3^3 =27 possibilities, while there are 6*6 =36 possible ordered sets.
Please check again