If a pair of dice are thrown repeatedly until a 7 is thrown, what is the probability that all the other possible numbers from 2 through 12 will have been thrown by the time the 7 has been thrown?
As a preliminary, what is the probability that 2, 11 and 12 will all have been thrown before the first 7?

well.....think we will have to apply the principle of "Bernoullian Sequence" for a finite number of trials in the given problem.....