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Register now and save up to $200 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 ## Of the 300 subjects who participated in an experiment using tagged by: ceilidh.erickson This topic has 4 expert replies and 0 member replies eitijan Master | Next Rank: 500 Posts Joined 30 Jan 2016 Posted: 157 messages Upvotes: 1 #### Of the 300 subjects who participated in an experiment using Mon Apr 25, 2016 5:38 am Of the 300 subjects who participated in an experiment using virtual-reality therapy to reduce their fear of heights, 40 percent experienced sweaty palms, 30 percent experienced vomiting, and 75 percent experienced dizziness. If all of the subjects experienced at least one of these effects and 35 percent of the subjects experienced exactly two of these effects, how many of the subjects experienced only one of these effects? (A) 105 (B) 125 (C) 130 (D) 180 (E) 195 Here , n(A u B u C)= n(A) + n(B) + n(C) - n(A n B) - n(B n C) - n(C n A) + n(A n B n C) A = 40% of 300 = 120 B = 30% of 300 = 90 C = 75% of 300 = 225 n(A n B) + n(B n C) + n(C n A) = 35% of 300 = 105 n(A u B u C) = 300 Putting values in above formula: 300 = 435 - 105 + n(A n B n C) 300 = 330 + n(A n B n C) n(A n B n C) = -30 What would be the next step? ### GMAT/MBA Expert Matt@VeritasPrep GMAT Instructor Joined 12 Sep 2012 Posted: 2637 messages Followed by: 114 members Upvotes: 625 Target GMAT Score: V51 GMAT Score: 780 Wed Apr 27, 2016 1:53 pm This is probably best done visually (with a Venn diagram): it's easy to lose track of the inclusion/exclusion equation if you try to do this sort of problem algebraically. Enroll in a Veritas Prep GMAT class completely for FREE. Wondering if a GMAT course is right for you? Attend the first class session of an actual GMAT course, either in-person or live online, and see for yourself why so many students choose to work with Veritas Prep. Find a class now! ### GMAT/MBA Expert ceilidh.erickson GMAT Instructor Joined 04 Dec 2012 Posted: 1787 messages Followed by: 229 members Upvotes: 1443 Mon Apr 25, 2016 8:26 am Here's another method, although it would take a bit longer: http://www.beatthegmat.com/plz-explain-official-guide-ps-q-178-t281640.html#738130 Usually, though, you won't need 7 variables; you'll just need 3. More here: http://www.beatthegmat.com/overlapping-sets-manhattan-gmat-cat-t288167.html#765098 _________________ Ceilidh Erickson Manhattan Prep GMAT & GRE instructor EdM in Mind, Brain, and Education Harvard Graduate School of Education Manhattan Prep instructors all have 99th+ percentile scores and expert teaching experience. Sign up for a FREE TRIAL, and learn why we have the highest ratings in the GMAT industry! Free Manhattan Prep online events - The first class of every online Manhattan Prep course is free. Classes start every week. ### GMAT/MBA Expert GMATGuruNY GMAT Instructor Joined 25 May 2010 Posted: 14044 messages Followed by: 1814 members Upvotes: 13060 GMAT Score: 790 Mon Apr 25, 2016 5:43 am _________________ Mitch Hunt GMAT Private Tutor 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. 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. ### GMAT/MBA Expert DavidG@VeritasPrep Legendary Member Joined 14 Jan 2015 Posted: 2667 messages Followed by: 120 members Upvotes: 1153 GMAT Score: 770 Mon Apr 25, 2016 6:19 am eitijan wrote: Of the 300 subjects who participated in an experiment using virtual-reality therapy to reduce their fear of heights, 40 percent experienced sweaty palms, 30 percent experienced vomiting, and 75 percent experienced dizziness. If all of the subjects experienced at least one of these effects and 35 percent of the subjects experienced exactly two of these effects, how many of the subjects experienced only one of these effects? (A) 105 (B) 125 (C) 130 (D) 180 (E) 195 Here , n(A u B u C)= n(A) + n(B) + n(C) - n(A n B) - n(B n C) - n(C n A) + n(A n B n C) A = 40% of 300 = 120 B = 30% of 300 = 90 C = 75% of 300 = 225 n(A n B) + n(B n C) + n(C n A) = 35% of 300 = 105 n(A u B u C) = 300 Putting values in above formula: 300 = 435 - 105 + n(A n B n C) 300 = 330 + n(A n B n C) n(A n B n C) = -30 What would be the next step? There are two versions of the three-set overlap equation. In the version you used, n(A u B u C)= n(A) + n(B) + n(C) - n(A n B) - n(B n C) - n(C n A) + n(A n B n C), the red portion refers to those in at least the two groups designated, not exactly those two groups. In other words, it's not correct to plug the 105 figure into that equation, because the 105 are in exactly two groups. The alternative version is Total=A+B+C-(sum of EXACTLY 2-group overlaps)-2âˆ-(all three)+Neither. This one would have been the appropriate equation to plug the 105 into. (And the fact that you ended up with a negative value is the clue that something is amiss.) _________________ Veritas Prep | GMAT Instructor Veritas Prep Reviews Save$100 off any live Veritas Prep GMAT Course

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