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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 ## If x-y+z=-1, -x+y+z=1, and x+y-z=-1, then x+y+z=? tagged by: BTGmoderatorLU ##### This topic has 3 expert replies and 0 member replies ### Top Member ## If x-y+z=-1, -x+y+z=1, and x+y-z=-1, then x+y+z=? If x-y+z=-1, -x+y+z=1, and x+y-z=-1, then x+y+z=? A. -2 B. -1 C. 0 D. 1 E. 2 The OA is B. I'm really confused with this PS question. Please, can any expert assist me with it? Thanks in advanced. ### GMAT/MBA Expert GMAT Instructor Joined 25 May 2010 Posted: 15381 messages Followed by: 1872 members Upvotes: 13060 GMAT Score: 790 LUANDATO wrote: If x-y+z=-1, -x+y+z=1, and x+y-z=-1, then x+y+z=? A. -2 B. -1 C. 0 D. 1 E. 2 Adding together the 3 equations, we get: (x-y+z) + (-x+y+z) + (x+y-z) = (-1) + 1 + (-1) (x-x+x) + (-y+y+y) + (z+z-z) = -1 x + y + z = -1. The correct answer is B. _________________ 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. ### GMAT/MBA Expert GMAT Instructor Joined 12 Sep 2012 Posted: 2635 messages Followed by: 117 members Upvotes: 625 Target GMAT Score: V51 GMAT Score: 780 We could also invoke the Lazy Testwriter Principle: the answers are probably friendly and/or small numbers, so try those. Let's start with x-y+z=-1 This looks like -1 - 0 + 0, so let's say x = -1, y = 0, and z = 0. If we plug those into our other two equations: -x + y + z => -(-1) + 0 + 0 => 1 and x + y - z => -1 + 0 - 0 => -1 They both check out, so we're set! 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 GMAT Instructor Joined 04 Oct 2017 Posted: 551 messages Followed by: 11 members Upvotes: 180 Quote: If x-y+z=-1, -x+y+z=1, and x+y-z=-1, then x+y+z=? A. -2 B. -1 C. 0 D. 1 E. 2 The OA is B. I'm really confused with this PS question. Please, can any expert assist me with it? Thanks in advanced. Hi LUANDATO, Let's take a look at your question. $$x-y+z=-1 ... (i)$$ $$-x+y+z=1... (ii)$$ $$x+y-z=-1 ... (iii)$$ $$x+y+z=?$$ Adding equations (i), (ii) and (iii), $$\left(x-y+z\right)+\left(-x+y+z\right)+\left(x+y-z\right)=-1+1-1$$ $$x-y+z-x+y+z+x+y-z=0-1$$ $$x-x+x-y+y+y+z+z-z=-1$$ $$x+y+z=-1$$ Therefore, Option B is correct. Hope it helps. I am available if you'd like any follow up. _________________ 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. • 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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