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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 ## The ratio of boys to girls in Class A is 3 to 4. The ratio ##### This topic has 3 expert replies and 0 member replies ### Top Member ## The ratio of boys to girls in Class A is 3 to 4. The ratio ## Timer 00:00 ## Your Answer A B C D E ## Global Stats Difficult The ratio of boys to girls in Class A is 3 to 4. The ratio of boys to girls in Class B is 4 to 5. If the two classes were combined, the ratio of boys to girls in the combined class would be 17 to 22. If Class A has one more boy and two more girls than class B, how many girls are in Class A? A. 8 B. 9 C. 10 D. 11 E. 12 OA E Source: Manhattan Prep ### GMAT/MBA Expert GMAT Instructor Joined 25 Apr 2015 Posted: 2852 messages Followed by: 18 members Upvotes: 43 Top Reply BTGmoderatorDC wrote: The ratio of boys to girls in Class A is 3 to 4. The ratio of boys to girls in Class B is 4 to 5. If the two classes were combined, the ratio of boys to girls in the combined class would be 17 to 22. If Class A has one more boy and two more girls than class B, how many girls are in Class A? A. 8 B. 9 C. 10 D. 11 E. 12 OA E Source: Manhattan Prep We can create the ratios: Class A: Boys : girls = 3x : 4x Class B: Boys : girls = 4y : 5y Combining, we have: (3x + 4y)/(4x + 5y) = 17/22 22(3x + 4y) = 17(4x + 5y) 66x + 88y = 68x + 85y 3y = 2x Also, we are given that class A has one more boy and two more girls than class B. So we have: 3x = 4y + 1 and 4x = 5y + 2 Since 3y = 2x, we know that 6y = 4x, and therefore we have: 6y = 5y + 2 y = 2 Since class A has 4x girls and 4x = 5y + 2, we have 5(2) + 2 = 12 girls in class A. Answer: E _________________ 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 ### GMAT/MBA Expert GMAT Instructor Joined 08 Dec 2008 Posted: 12999 messages Followed by: 1250 members Upvotes: 5254 GMAT Score: 770 Top Reply BTGmoderatorDC wrote: The ratio of boys to girls in Class A is 3 to 4. The ratio of boys to girls in Class B is 4 to 5. If the two classes were combined, the ratio of boys to girls in the combined class would be 17 to 22. If Class A has one more boy and two more girls than class B, how many girls are in Class A? A. 8 B. 9 C. 10 D. 11 E. 12 OA E Source: Manhattan Prep The ratio of boys to girls in Class A is 3 to 4. Let B = number of boys in class A Let G = number of girls in class A We get: B/G = 3/4 Cross multiply to get: 4B = 3G Class A has one more boy and two more girls than class B So B - 1 = number of boys in class B So G - 2 = number of girls in class B The ratio of boys to girls in Class B is 4 to 5 We get: (B - 1)/(G - 2) = 4/5 Cross multiply to get: 5(B - 1) = 4(G - 2) Expand: 5B - 5 = 4G - 8 So, we now have the following system to solve for G: 4B = 3G 5B - 5 = 4G - 8 Take 4B = 3G and solve for B to get: B = 3G/4 Take 5B - 5 = 4G - 8 and replace B with 3G/4 We get: 5(3G/4) - 5 = 4G - 8 Expand: 15G/4 - 5 = 4G - 8 Multiply both sides by 4 to get: 15G - 20 = 16G - 32 Solve to get: G = 12 Answer: E RELATED VIDEOS - Intro to ratios: https://www.gmatprepnow.com/module/gmat-arithmetic/video/1081 _________________ Brent Hanneson â€“ Creator of GMATPrepNow.com Use my video course along with Sign up for free Question of the Day emails And check out all of these 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: 15361 messages Followed by: 1865 members Upvotes: 13060 GMAT Score: 790 BTGmoderatorDC wrote: The ratio of boys to girls in Class A is 3 to 4. The ratio of boys to girls in Class B is 4 to 5. If the two classes were combined, the ratio of boys to girls in the combined class would be 17 to 22. If Class A has one more boy and two more girls than class B, how many girls are in Class A? A. 8 B. 9 C. 10 D. 11 E. 12 We can PLUG IN THE ANSWERS, which represent the number of girls in Class A. Since b:g = 3:4, the number of girls must be a multiple of 4. Eliminate B, C and D. Answer choice A: g = 8. Since b:g = 3:4 = 6:8, b=6. Since Class A has one more boy and two more girls than Class B, in Class B, b=5 and g=6. Doesn't work: the required ratio in Class B is 4:5. Eliminate A. The correct answer is E. _________________ 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. 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