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100 points for $49 worth of Veritas practice GMATs FREE VERITAS PRACTICE GMAT EXAMS Earn 10 Points Per Post Earn 10 Points Per Thanks Earn 10 Points Per Upvote In nine independent trials, what is the probability that tagged by: BTGmoderatorLU This topic has 1 expert reply and 1 member reply Top Member In nine independent trials, what is the probability that Timer 00:00 Your Answer A B C D E Global Stats Difficult Source: Magoosh 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. The OA is D GMAT/MBA Expert GMAT Instructor Joined 22 Aug 2016 Posted: 1975 messages Followed by: 30 members Upvotes: 470 BTGmoderatorLU wrote: Source: Magoosh 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. The OA is D Instead of calculating the probability that Outcome A happens at least once, it's better we calculate the probability that Outcome A does not happen even once; once we get this value, we would deduct it from 1 and get the answer. Probability that Outcome A happens at least once = 1 - Probability that Outcome A does not happen even once in 9 trials Let's take each statement one by one. 1) The probability that Outcome A does not happen even once in any of the nine trials is 0.026. => Probability that Outcome A happens at least once = 1 - Probability that Outcome A does not happen even once in 9 trials = 1 - 0.026 = A unique value. Sufficient. 2) The probability of Outcome A resulting in a single trial is 1/3. Probability that Outcome A does not happen in a single trial = 1 - 1/3 = 2/3 Probability that Outcome A does not happen even once in 9 trials = (2/3)^9 Probability that Outcome A happens at least once = 1 - (2/3)^9 = A unique value. Sufficient. The correct answer: D Hope this helps! -Jay _________________ Manhattan Review GMAT Prep Locations: GRE Manhattan | ACT Prep Courses San Francisco | IELTS Prep Courses Boston | Seattle IELTS Tutoring | and many more... Schedule your free consultation with an experienced GMAT Prep Advisor! Click here. Top Member Legendary Member Joined 02 Mar 2018 Posted: 1104 messages Followed by: 2 members Probability of favorable outcome + probability of unfavorable outcome = 1 Probability of favorable outcome = 1 - probability of favorable outcome Probability that outcome A happens at least once = 1 - probability that outcome A never happens Statement 1 The probability that outcome A doesn't even happen even once in any of the nine trials is 0.026 Probability that outcome A happens at least once = 1 - 0.026 = 0.974 Statement 1 is SUFFICIENT. Statement 2 The probability of outcome A resulting in a single trial is 1/3 The probability that the outcome doesn't happen in a single trial. $$\frac{1}{1}-\frac{1}{3}=\frac{3-1}{3}=\frac{2}{3}$$ Probability that the outcome A happens in all the 9 trials $$\left(\frac{2}{3}\right)^9=\frac{2^9}{3^9}=\frac{512}{19683}=0.026$$ Probability that outcome A happens at least once = 1- 0.026 = 0.974 Statement 2 is also SUFFICIENT. Both statement alone are SUFFICIENT. $$answer\ is\ Option\ D$$ • 5-Day Free Trial 5-day free, full-access trial TTP Quant Available with Beat the GMAT members only code • Free Trial & Practice Exam BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Award-winning private GMAT tutoring Register now and save up to$200

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