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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 his ranch, Doug Bo can place a loop of rope, called a... tagged by: BTGmoderatorLU ##### This topic has 1 expert reply and 0 member replies ### Top Member ## In his ranch, Doug Bo can place a loop of rope, called a... In his ranch, Doug Bo can place a loop of rope, called a lasso, once in every 2 throws around a cow's neck. What is the probability that he will be able to place a lasso around a cow's neck at least once in 5 attemps? (A) 1/5 (B) 15/32 (C) 1/2 (D) 31/32 (E) 1 The OA is D. I'm confused with this PS question. Experts, any suggestion about how can I solve it? Thanks in advance. ### GMAT/MBA Expert Legendary Member Joined 14 Jan 2015 Posted: 2667 messages Followed by: 122 members Upvotes: 1153 GMAT Score: 770 LUANDATO wrote: In his ranch, Doug Bo can place a loop of rope, called a lasso, once in every 2 throws around a cow's neck. What is the probability that he will be able to place a lasso around a cow's neck at least once in 5 attemps? (A) 1/5 (B) 15/32 (C) 1/2 (D) 31/32 (E) 1 The OA is D. I'm confused with this PS question. Experts, any suggestion about how can I solve it? Thanks in advance. First, P(x) = 1 - P(Not x) So, P(at least one success in five attempts) = 1 - P(no successes in five attempts) If Doug Bo succeeds once every two tosses, we know the probability is 1/2 that each attempt is successful. (And the probability of failure is also 1/2) P(no successes in five attempts) = (1/2) * (1/2) * (1/2) * (1/2) * (1/2) = 1/32 1 - P(no successes in five attempts) = 1 - 1/32 = 31/32. The answer is D _________________ Veritas Prep | GMAT Instructor Veritas Prep Reviews Save$100 off any live Veritas Prep GMAT Course

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