Bunuel wrote:
In nine independent trials, what is the probability that Outcome A happens at least once?
(1) The probability that Outcome A does not happen even once in any of the nine trials is 0.026
(2) the probability of Outcome A resulting in a single trial is 1/3.
Kudos for a correct solution.
MAGOOSH OFFICIAL SOLUTIONWe know there are nine trials. To figure out the probability that Outcome A happens
at least once, we would need a way to figure out the probability of A, P(A).
Statement #1: this statement gives us the complement. The complement of (Outcome A happens at least once) is (Outcome A does not happen at all). Complementary probabilities have a sum of 1 — P(not K) = 1 – P(K). Therefore, using the complement rule, we could figure out that
P(A happens at least once) = 1 – P(A doesn’t happen at all) = 1 – 0.026 = 0.974
This information allows us to answer the prompt question. This statement, alone and by itself, is sufficient.
Statement #2: this statement gives us P(A), which would allow us to calculate the probability that A happens at least once in nine trials. This statement, alone and by itself, is sufficient.
Both statement sufficient. Answer = D
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http://magoosh.com/gmat/2013/gmat-data- ... JzRXH.dpuf _________________