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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 ## Probability Query ##### This topic has 4 member replies ## Probability Query Can someone help me understand this question : n question are either true or false. What is the minimum value of n for which (p) of all true <1/1000? thanx Legendary Member Joined 17 May 2011 Posted: 1448 messages Followed by: 53 members Upvotes: 375 Hi, Probability that each each question is correct is 1/2. So, probability of gettign all 'n' questions correct is (1/2)^n So, (1/2)^n < 1/1000 => 2^n > 1000 2^10 = 1024 So, n >= 10 Minimum value of n is 10. _________________ Cheers! Things are not what they appear to be... nor are they otherwise Last edited by Frankenstein on Thu Jun 30, 2011 8:33 pm; edited 1 time in total Senior | Next Rank: 100 Posts Joined 22 Aug 2008 Posted: 33 messages Upvotes: 1 Frankenstein wrote: Hi, Probability that each each question is correct is 1/2. So, probability of gettign all 'n' questions correct is (1/2)^n So, (1/2)^n < 1000 => 2^n > 1000 2^10 = 1024 So, n >= 10 Minimum value of n is 10. Can you please explain this stmt - "So, (1/2)^n < 1000 => 2^n > 1000" _________________ Thanks! - Treker Legendary Member Joined 17 May 2011 Posted: 1448 messages Followed by: 53 members Upvotes: 375 treker wrote: Frankenstein wrote: Hi, Probability that each each question is correct is 1/2. So, probability of gettign all 'n' questions correct is (1/2)^n So, (1/2)^n < 1000 => 2^n > 1000 2^10 = 1024 So, n >= 10 Minimum value of n is 10. Can you please explain this stmt - "So, (1/2)^n < 1000 => 2^n > 1000" Hi, That was a typo. I have edited now. If you are interested in the underlying principle, If a and b are positive and a > b, then 1/a < 1/b. Example: 3>2 .. 1/3 < 1/2. _________________ Cheers! Things are not what they appear to be... nor are they otherwise Master | Next Rank: 500 Posts Joined 10 May 2011 Posted: 461 messages Followed by: 3 members Upvotes: 36 probability of having a right or wrong in question = 1/2 thus 1/2^n < 1/1000 is what being asked here. hence 2^n = 1024 is sufficient meaning n = 10. _________________ For Understanding Sustainability,Green Businesses and Social Entrepreneurship visit -https://aamthoughts.blogspot.com/ (Featured Best Green Site Worldwide-https://bloggers.com/green/popular/page2) • 5-Day Free Trial 5-day free, full-access trial TTP Quant 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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