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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 ## Which of the following is NOT a factor of 20! ? tagged by: Vincen ##### This topic has 2 expert replies and 0 member replies ### Top Member ## Which of the following is NOT a factor of 20! ? Which of the following is NOT a factor of 20! ? I. 29 II. 85 III. 121 A. I only B. II only C. III only D. I and II E. I and III The OA is E. Is there a fast way to get the correct answer here? Experts, can you show me how would you solve it? Thanks in advanced. ### GMAT/MBA Expert GMAT Instructor Joined 04 Oct 2017 Posted: 551 messages Followed by: 11 members Upvotes: 180 Top Reply Hello Vincen. Let's take a look at your question. Option 1) 29. This is a prime number and it does not appear in 20! So, this is not be a factor. Option 2) 85. 85=5*17, and 5 and 17 are in 20! So, 85 is a factor. Option 3) 121. 121=11*11, but in 20! there is only one 11. So, this is not be a factor. Therefore, the correct answer is E. I hope this explanation may help you. I'm available if you'd like a follow-up. 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 GMAT Instructor Joined 09 Apr 2015 Posted: 1465 messages Followed by: 19 members Upvotes: 39 Vincen wrote: Which of the following is NOT a factor of 20! ? I. 29 II. 85 III. 121 A. I only B. II only C. III only D. I and II E. I and III Since 20! does not contain a prime factor of 29, 29 is not a factor of 20! Since 85 = 17 x 5, and 20! contains both prime factors of 17 and 5, 85 is a factor of 20!. Since 121 = 11^2, and 20! does not have 2 prime factors of 11, 121 is not a factor 20!. Answer: E _________________ 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 • 5 Day FREE Trial Study Smarter, Not Harder Available with Beat the GMAT members only code • FREE GMAT Exam Know how you'd score today for$0

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