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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 What is the probability of getting only 1 head in a single tagged by: M7MBA This topic has 3 expert replies and 0 member replies Top Member What is the probability of getting only 1 head in a single What is the probability of getting only 1 head in a single throw of three fair coins? A) 1/2 B) 3/8 C) 1/4 D) 1/5 E) 5/8 The OA is the option B. How can I determine the correct answer? Shouldn't it be (1/2)^3=1/8? I am confused. GMAT/MBA Expert GMAT Instructor Joined 04 Oct 2017 Posted: 551 messages Followed by: 11 members Upvotes: 180 M7MBA wrote: What is the probability of getting only 1 head in a single throw of three fair coins? A) 1/2 B) 3/8 C) 1/4 D) 1/5 E) 5/8 The OA is the option B. How can I determine the correct answer? Shouldn't it be (1/2)^3=1/8? I am confused. Hi M7MBA. Let's take a look at your question. First, we have _ _ _ (3) places, and each place has 2 possibilities (H or T). Hence, there are a total of 2*2*2=8 possibilities. Now, we want to obtain ONLY one head, this implies that we have the next cases: HTT THT TTH Therefore, there are 3 cases. Finally, the answer is cases favorable / total of cases = 3/8. This is why the correct answer is B. I hope this answer may help you. Feel free to ask me again if you have any doubt. Regards. _________________ GMAT Prep From The Economist We offer 70+ point score improvement money back guarantee. Our average student improves 98 points. Free 7-Day Test Prep with Economist GMAT Tutor - Receive free access to the top-rated GMAT prep course including a 1-on-1 strategy session, 2 full-length tests, and 5 ask-a-tutor messages. Get started now. GMAT/MBA Expert Elite Legendary Member Joined 23 Jun 2013 Posted: 10197 messages Followed by: 497 members Upvotes: 2867 GMAT Score: 800 Hi M7MBA, Since we're tossing just 3 coins, there aren't that many possible outcomes. This question can be solved simply by listing out the possibilities and answering the exact question that is asked. With 3 coins, there are (2)(2)(2) = 8 possible outcomes. They are... HHH HHT HTH THH TTT TTH THT HTT We're asked for the probability of getting exactly 1 HEAD from those 3 tosses. There are three ways (out of 8 total) to get exactly 2 heads (HTT, THT and TTH). Final Answer: B GMAT assassins aren't born, they're made, Rich _________________ Contact Rich at Rich.C@empowergmat.com GMAT/MBA Expert GMAT Instructor Joined 09 Apr 2015 Posted: 1465 messages Followed by: 19 members Upvotes: 39 M7MBA wrote: What is the probability of getting only 1 head in a single throw of three fair coins? A) 1/2 B) 3/8 C) 1/4 D) 1/5 E) 5/8 We need to determine the probability of H-T-T = 1/2 x 1/2 x 1/2 = 1/8. Since H-T-T can be arranged in 3!/2! = 3 ways, the total probability is 3/8. Answer: B _________________ Jeffrey Miller Head of GMAT Instruction jeff@targettestprep.com See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews • 1 Hour Free BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Free Veritas GMAT Class Experience Lesson 1 Live Free Available with Beat the GMAT members only code • Get 300+ Practice Questions 25 Video lessons and 6 Webinars for FREE Available with Beat the GMAT members only code • 5-Day Free Trial 5-day free, full-access trial TTP Quant Available with Beat the GMAT members only code • 5 Day FREE Trial Study Smarter, Not Harder Available with Beat the GMAT members only code • Free Trial & Practice Exam BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Magoosh Study with Magoosh GMAT prep Available with Beat the GMAT members only code • FREE GMAT Exam Know how you'd score today for$0

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