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counting and probability senior

Problem

Positive integers , , and are randomly and independently selected with replacement from the set . What is the probability that is divisible by ?
(A)
(B)
(C)
(D)
(E)
Solution
We group this into groups of , because . This means that every residue class mod 3 has an equal probability. If , we are done. There is a probability of that that happens. Otherwise, we have , which means that . So either or which will lead to the property being true. There is a chance for each bundle of cases to be true. Thus, the total for the cases is . But we have to multiply by because this only happens with a chance. So the total is actually . The grand total is
Final answer
E