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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 ## In a certain school, there are 160 boys and 240 girls. If 15 ##### This topic has 3 expert replies and 1 member reply ### Top Member ## In a certain school, there are 160 boys and 240 girls. If 15 ## Timer 00:00 ## Your Answer A B C D E ## Global Stats Difficult In a certain school, there are 160 boys and 240 girls. If 15 percent of the boys are left-handed and 25 percent of the girls are left-handed, what percent of the schools entire student population is left-handed? A. 18 B. 20 C. 21 D. 23 E. 24 OA C Source: Magoosh ### GMAT/MBA Expert GMAT Instructor Joined 25 Apr 2015 Posted: 2852 messages Followed by: 18 members Upvotes: 43 Top Reply BTGmoderatorDC wrote: In a certain school, there are 160 boys and 240 girls. If 15 percent of the boys are left-handed and 25 percent of the girls are left-handed, what percent of the schools entire student population is left-handed? A. 18 B. 20 C. 21 D. 23 E. 24 OA C Source: Magoosh 160 x 0.15 = 24 left-handed boys 240 x 0.25 = 60 left-handed girls Thus, 84/400 x 100 = 21/100 x 100 = 21 percent of the entire population is left-handed. Answer: C _________________ Scott Woodbury-Stewart Founder and CEO scott@targettestprep.com See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews ### Top Member Legendary Member Joined 02 Mar 2018 Posted: 1121 messages Followed by: 2 members Top Reply Total no of boys = 160 Left handed boys = 15% of the total boys =24 boys $$=\frac{15}{100}\cdot160$$ Total no of girls = 240 Left hande girls = 25% of the total girls. $$=\frac{25}{100}\cdot240\ =60girls$$ $$=\frac{25}{100}\cdot240\ =60girls$$ Total left handed students in the school = Left handed boys + Left handed girls = 24 + 60 = 84 students Students entire population = 160 + 240 = 400 % of left handed students in the school $$\frac{84}{100}\cdot100=21\%$$ $$answer\ is\ Option\ C$$ ### GMAT/MBA Expert GMAT Instructor Joined 02 Jun 2008 Posted: 2475 messages Followed by: 351 members Upvotes: 1090 GMAT Score: 780 This is a weighted average problem, where 15% and 25% are the averages of each group. We can draw a number line with the three averages: ---15------------A------25--- Since the ratio of boys to girls is 2 to 3, the overall average A will divide the total distance above in a 3 to 2 ratio, so the larger distance, from 15 to A, is 3/5 of the total distance between 15 and 25, so that distance is 6 and A = 15 + 6 = 21. I'm using a weighted average method sometimes called 'alligation' here - someone unfamiliar with that method might not follow the logic above, but can read about the method by googling that term. For this particular problem, it's straightforward to solve arithmetically, though the method above is a better method for harder questions. Here we have (3/20)(160) = 24 lefthanded boys, (1/4)(240) = 60 lefthanded girls, and 400 students in total, so the answer is (24+60)/400 = 84/400 = 21/100 = 21%. _________________ 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 ### GMAT/MBA Expert GMAT Instructor Joined 25 May 2010 Posted: 15362 messages Followed by: 1866 members Upvotes: 13060 GMAT Score: 790 BTGmoderatorDC wrote: In a certain school, there are 160 boys and 240 girls. If 15 percent of the boys are left-handed and 25 percent of the girls are left-handed, what percent of the school`s entire student population is left-handed? A. 18 B. 20 C. 21 D. 23 E. 24 Left-handed boys = 15% of 160 = 24. Left-handed girls = 25% of 240 = 60. (total left-handed)/(total students) = (24+60)/(160+240) = 84/400 = 21/100 = 21%. The correct answer is C. _________________ 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. • 5-Day Free Trial 5-day free, full-access trial TTP Quant Available with Beat the GMAT members only code • 5 Day FREE Trial Study Smarter, Not Harder Available with Beat the GMAT members only code • 1 Hour Free BEAT THE GMAT EXCLUSIVE 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 GMAT Exam Know how you'd score today for$0

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