Suppose that an experiment has four possible outcomes: A, B, C, and D. If P(A) = P(B) = P(C) and

P(D) = 2P(A), what is the probability of each event?

Total probability = 1, so all the possible outcomes must sum to 1. Since P(D) = 2P(A),

P(3A + B + C) = 1

Remember that A = B = C.

I hope this helps. Thanks for asking.