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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 ## If a coin has an equal probability of landing heads up or ta ##### This topic has 2 expert replies and 1 member reply ### Top Member ## If a coin has an equal probability of landing heads up or ta ## Timer 00:00 ## Your Answer A B C D E ## Global Stats Difficult If a coin has an equal probability of landing heads up or tails up each time it is flipped , what is the probability that the coin will land heads up exectly twice in 3 consecutive flips ? A. 0.125 B. 0.25 C. 0.375 D. 0.5 E. 0.666 OA C Source: GMAT Prep ### Top Member Legendary Member Joined 02 Mar 2018 Posted: 1121 messages Followed by: 2 members Top Reply The probability of coin landing heads up twice in three consecutive flips will have three possibilities. $$HHT,\ HTH\ or\ THH$$ $$HHT=\frac{1}{2}\cdot\frac{1}{2}\cdot\frac{1}{2}=\frac{1}{8}$$ $$HTH=\frac{1}{2}\cdot\frac{1}{2}\cdot\frac{1}{2}=\frac{1}{8}$$ $$THH=\frac{1}{2}\cdot\frac{1}{2}\cdot\frac{1}{2}=\frac{1}{8}$$ Add up the three $$\frac{1}{8}+\frac{1}{8}+\frac{1}{8}=\frac{3}{8}=0.375$$ $$answer\ is\ Option\ C$$ ### GMAT/MBA Expert GMAT Instructor Joined 25 Apr 2015 Posted: 2852 messages Followed by: 18 members Upvotes: 43 Top Reply BTGmoderatorDC wrote: If a coin has an equal probability of landing heads up or tails up each time it is flipped , what is the probability that the coin will land heads up exectly twice in 3 consecutive flips ? A. 0.125 B. 0.25 C. 0.375 D. 0.5 E. 0.666 OA C Source: GMAT Prep We need to determine the probability of HHT and its variations: P(HHT) = (1/2)^3 = 1/8 Since we can arrange HHT in 3!/2! = 3 ways, the overall probability is 3 x 1/8 = 3/8 = 0.375. Answer: C _________________ Scott Woodbury-Stewart Founder and CEO scott@targettestprep.com See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews ### GMAT/MBA Expert GMAT Instructor Joined 25 May 2010 Posted: 15362 messages Followed by: 1866 members Upvotes: 13060 GMAT Score: 790 BTGmoderatorDC wrote: If a coin has an equal probability of landing heads up or tails up each time it is flipped , what is the probability that the coin will land heads up exectly twice in 3 consecutive flips ? A. 0.125 B. 0.25 C. 0.375 D. 0.5 E. 0.666 P(H) = 1/2. P(T) = 1/2. One way to get exactly 1 heads in 3 flips: P(HTT) = 1/2 * 1/2 * 1/2 = 1/8. Since H can appear in a total of 3 positions -- 1st flip, 2nd flip, or 3rd flip -- we multiply by 3: 1/8 * 3 = 3/8 = 0.375. The correct answer is C. _________________ Mitch Hunt Private Tutor for the GMAT and GRE GMATGuruNY@gmail.com If you find one of my posts helpful, please take a moment to click on the "UPVOTE" icon. Available for tutoring in NYC and long-distance. For more information, please email me at GMATGuruNY@gmail.com. Student Review #1 Student Review #2 Student Review #3 Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now. • Award-winning private GMAT tutoring Register now and save up to$200

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