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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 A physics class has majors and non-majors in a ratio of... tagged by: BTGmoderatorLU This topic has 3 expert replies and 0 member replies Top Member A physics class has majors and non-majors in a ratio of... A physics class has majors and non-majors in a ratio of 4 to 10. If two more majors were to be added to the class, the ratio would then be 2 to 4. How many people are in the class? A. 14 B. 28 C. 42 D. 56 E. 70 The OA is B. I'm confused by this PS question. If the initial ratio is 4/10, then (4+2)/10=2/4. I stuck here. Experts, any suggestion? Thanks in advance. GMAT/MBA Expert GMAT Instructor Joined 08 Dec 2008 Posted: 12422 messages Followed by: 1244 members Upvotes: 5254 GMAT Score: 770 LUANDATO wrote: A physics class has majors and non-majors in a ratio of 4 to 10. If two more majors were to be added to the class, the ratio would then be 2 to 4. How many people are in the class? A. 14 B. 28 C. 42 D. 56 E. 70 The ratio of the number of physics majors to non-physics majors is 3 to 5 Let P = number of Physics majors Let N = number of Non-physics majors So, we get: P/N = 3/5 Cross multiply to get: 5P = 3N Rearrange to get: 5P - 3N = 0 If two of the physics majors were to change their major to biology, the new ratio of physics majors to non-physics majors would be 1 to 2 This means that P - 2 = the NEW number of Physics majors And N + 2 = the NEW number of Non-physics majors So, we get: (P - 2)/(N + 2) = 1/2 Cross multiply to get: 2(P - 2) = 1(N + 2) Expand: 2P - 4 = N + 2 Rearrange to get: 2P - N = 6 We now have two equations: 5P - 3N = 0 2P - N = 6 Multiply BOTTOM equation by 3 to get: 5P - 3N = 0 6P - 3N = 18 Subtract top equation from bottom to get: P = 18 Answer: B 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! GMAT/MBA Expert GMAT Instructor Joined 25 May 2010 Posted: 14929 messages Followed by: 1855 members Upvotes: 13060 GMAT Score: 790 LUANDATO wrote: A physics class has majors and non-majors in a ratio of 4 to 10. If two more majors were to be added to the class, the ratio would then be 2 to 4. How many people are in the class? A. 14 B. 28 C. 42 D. 56 E. 70 We can PLUG IN THE ANSWERS, which present the total number of people in the class. Let P = physics majors and N = non-physics majors. When the correct answer is plugged in, adding 2 physics majors will yield the following ratio: (New P)/N = 2/4 = 1/2. B: total = 28 In this case: Since P:N = 4:10 = 8:20, P=8 and N=20, with the result that the total number of students = 8+20 = 28. After 2 physics majors are added -- increasing the value of P from 8 to 10 -- we get: (new P)/N = 10/20 = 1/2. Success! 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 25 Apr 2015 Posted: 1776 messages Followed by: 14 members Upvotes: 43 LUANDATO wrote: A physics class has majors and non-majors in a ratio of 4 to 10. If two more majors were to be added to the class, the ratio would then be 2 to 4. How many people are in the class? A. 14 B. 28 C. 42 D. 56 E. 70 We see that the ratio of majors to non-majors = 4x : 10x. When two more majors were to be added to the class, the ratio would then be 2 to 4, and thus: (4x + 2)/10x = 2/4 4(4x + 2) = 20x 16x + 8 = 20x 8 = 4x 2 = x So there are 4(2) + 10(2) = 28 people in the class. Answer: B _________________ Scott Woodbury-Stewart Founder and CEO • 5-Day Free Trial 5-day free, full-access trial TTP Quant 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 • Award-winning private GMAT tutoring Register now and save up to$200

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