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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 ## Sets tagged by: Brent@GMATPrepNow ##### This topic has 3 expert replies and 3 member replies ## Sets In a School, 250 students participate in debate or student government of both. If 40 of these students participate in both debate and student government, how many of these students do not participate in debate? (1) 80 of the students do not participate in student government. (2) In a School, 150 students do not participate in either debate or student government. OA is A P.S.-According to me,it is C using formula;Total=only A+ only B-Both+Neither ### GMAT/MBA Expert GMAT Instructor Joined 02 Jun 2008 Posted: 2354 messages Followed by: 348 members Upvotes: 1090 GMAT Score: 780 We want to know how many of the 250 students mentioned in the stem are in student government but not in debate (everyone is in at least one of the two groups, so if someone is not in debate, he or she must be in government only). Using Statement 1, we know 80 are not in government, so the rest, or 250 - 80 = 170, must be in government. The stem tells us that 40 of these people are also in debate, so the rest, or 170 - 40 = 130, are not in debate. I'd use a Venn diagram, but that's a bit hard to draw here! If you were trying to use a formula here when only looking at Statement 1, notice that the 250 in the question does not include the 'neither' group. So 250 is only equal to the "only A + only B + both" part of your formula (and the minus sign in your formula in front of "Both" needs to be a plus sign). When you use Statement 2, you discover that Neither = 150, and the Total is therefore 400 (not 250), but we don't need that information to answer the question. _________________ If you are looking for online GMAT math tutoring, or if you are interested in buying my advanced Quant books and problem sets, please contact me at ianstewartgmat at gmail.com Master | Next Rank: 500 Posts Joined 17 Oct 2010 Posted: 363 messages Followed by: 3 members Upvotes: 115 tapanmittal wrote: In a School, 250 students participate in debate or student government of both. If 40 of these students participate in both debate and student government, how many of these students do not participate in debate? (1) 80 of the students do not participate in student government. (2) In a School, 150 students do not participate in either debate or student government. OA is A P.S.-According to me,it is C using formula;Total=only A+ only B-Both+Neither Total students = Debate only + Government only + Both + Neither 250 = D + G + DG + 0 = D + G + GB = D + G + 40 If a student does not participate in debate, it means he participate in government only therefore the question "how many of these students do not participate in debate" means how many students particpate in government only? What is G in equation? (1) 80 of the students do not participate in student government therefore 80 students particpate in debate only 250 = D + G + 40 = 80 + G + 40 250 = 120 + G G = 130 statement is sufficent (2) In a School, 150 students do not participate in either debate or student government Total students = Debate only + Government only + Both + Neither 250 + 150 = D + G + DG + neither = D + G + GB + 150 = D + G + 40 + 150 400 = D + G + 190 We cant find G because we dont know D. Therfore statement is insufucient Answer = A ### GMAT/MBA Expert GMAT Instructor Joined 25 May 2010 Posted: 15257 messages Followed by: 1861 members Upvotes: 13060 GMAT Score: 790 A clearer wording might be as follows: tapanmittal wrote: In School X, a total of 250 students are members of Club Y. Every member of Club Y participates in debate or student government or both. If 40 members of Club Y participate in both debate and student government, how many members of Club Y do not participate in debate? (1) 80 members of Club Y do not participate in student government. (2) In School X, 150 students do not participate in either debate or student government. Since the 250 members participate in debate or government or both, we get: Only Debate + Only Government + Both = 250. Since 40 members participate in both, we get: Only Debate + Only Government + 40 = 250 Only Debate + Only Government = 210. To determine how many members do not participate in debate -- in other words, to determine how many participate only in government -- we need to know how many participate only in debate. Question stem, rephrased: How many members of Club Y participate only in debate? Statement 1: 80 members of Club Y do not participate in student government. Implication: These 80 members participate only in debate. SUFFICIENT. Statement 2: In School X, 150 students do not participate in either debate or student government. Implication: Since every member of Club Y participates in debate or student government or both, these 150 students are not members of Club Y. No way to determine how many members of Club Y participate only in debate. INSUFFICIENT. The correct answer is A. _________________ 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. Legendary Member Joined 07 Aug 2014 Posted: 510 messages Followed by: 5 members Upvotes: 3 Hi Experts , Can you please explain this question by Double Matrix. Thanks. Newbie | Next Rank: 10 Posts Joined 23 Feb 2015 Posted: 3 messages Option2: No info about club Y students. Therefore answer is A ### GMAT/MBA Expert GMAT Instructor Joined 08 Dec 2008 Posted: 12831 messages Followed by: 1247 members Upvotes: 5254 GMAT Score: 770 I thought I'd point out that iwgi's approach (known as the Double Matrix Method) can be used for most questions featuring a population in which each member has two characteristics associated with it. Here, we have a population of students, and the two characteristics are: - participates in debate or doesn't participate in debate - participates in student government or doesn't participate in student government This question type is VERY COMMON on the GMAT, so be sure to master the technique. To learn more about the Double Matrix Method, watch our free video: http://www.gmatprepnow.com/module/gmat-word-problems?id=919 Once youâ€™re familiar with this technique, you can attempt these additional practice questions: Easy Problem Solving questions - http://www.beatthegmat.com/the-aam-aadmi-party-t272242.html - http://www.beatthegmat.com/finance-majors-non-finance-majors-overlapping-set-question-t167425.html Medium Problem Solving questions - http://www.beatthegmat.com/probability-question-t273360.html - http://www.beatthegmat.com/posted-speed-limit-t272374.html - http://www.beatthegmat.com/motel-t271938.html - http://www.beatthegmat.com/of-the-applicants-passes-a-certain-test-15-t270255.html - http://www.beatthegmat.com/opening-night-and-late-patrons-t264869.html - http://www.beatthegmat.com/at-least-100-students-at-a-certain-high-school-study-japanes-t274669.html - http://www.beatthegmat.com/prblem-solving-t279424.html Difficult Problem Solving questions - http://www.beatthegmat.com/ratio-problem-t268339.html - http://www.beatthegmat.com/overlapping-sets-question-t265223.html - http://www.beatthegmat.com/fractions-t264254.html - http://www.beatthegmat.com/overlapping-sets-t264092.html - http://www.beatthegmat.com/mba/2011/05/09/random-double-matrix-question-2 Easy Data Sufficiency questions - http://www.beatthegmat.com/for-what-percent-of-those-tested-for-a-certain-t270596.html - http://www.beatthegmat.com/ds-quest-t187706.html Medium Data Sufficiency questions - http://www.beatthegmat.com/sets-matrix-ds-t271914.html - http://www.beatthegmat.com/each-of-people-voted-once-in-an-election-x-t271375.html - http://www.beatthegmat.com/a-manufacturer-t270331.html - http://www.beatthegmat.com/in-costume-for-halloween-t269355.html - http://www.beatthegmat.com/mba/2011/05/05/random-double-matrix-question-1 Difficult Data Sufficiency questions - http://www.beatthegmat.com/double-set-matrix-question-t271423.html - http://www.beatthegmat.com/sets-t269449.html - http://www.beatthegmat.com/mba/2011/05/16/random-double-matrix-question-3 Cheers, Brent _________________ Brent Hanneson â€“ Creator of GMATPrepNow.com Use our video course along with Sign up for our free Question of the Day emails And check out all of our free resources GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMATâ€™s FREE 60-Day Study Guide and reach your target score in 2 months! • Free Trial & Practice Exam BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • 5 Day FREE Trial Study Smarter, Not Harder 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 • Free Practice Test & Review How would you score if you took the GMAT Available with Beat the GMAT members only code • 1 Hour Free BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Award-winning private GMAT tutoring Register now and save up to$200

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