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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 ## What is the average (arithmetic mean) of A, B, and 4C? tagged by: M7MBA ##### This topic has 1 expert reply and 2 member replies ### Top Member ## What is the average (arithmetic mean) of A, B, and 4C? What is the average (arithmetic mean) of A, B, and 4C? (1) A + B = 17 (2) C^2 = 49 The OA is the option E. Using both statements together is not sufficient to get an answer? Experts, can you show me what is the best way to solve this PS question? ### Top Member Legendary Member Joined 07 Sep 2017 Posted: 833 messages Followed by: 3 members Upvotes: 6 Hello Gmat_mission. We are asked for $$\frac{A+B+4C}{3}=?$$ (1) A+B=17. This implies that $$\frac{A+B+4C}{3}=\frac{17+4C}{3}=?$$ Hence, we cannot determine the average. $$\left(2\right)\ \ C^2=49.$$ This implies that C=7 or C=-7. Hence we get $$\frac{A+B+4C}{3}=\frac{A+B+4\left(\pm7\right)}{3}=\frac{A+B\pm28}{3}=?$$ Hence, we cannot determine the average. Using both statements together we get $$\frac{A+B+4C}{3}=\frac{17\pm28}{3}.$$ We have two options $$\frac{A+B+4C}{3}=\frac{17+28}{3}=\frac{45}{3}=15$$ or $$\frac{A+B+4C}{3}=\frac{17-28}{3}=-\frac{11}{3}.$$ Since the options are different, hence this option is NOT sufficient. Therefore, the correct answer is E. ### Top Member Legendary Member Joined 02 Mar 2018 Posted: 1171 messages Followed by: 2 members $$mean\ of\ A,\ B\ and\ 4C\ is\ =\frac{A+B+4C}{3}$$ $$If\ c^2=49$$ $$then\ c=\sqrt{49}=\left(\frac{+}{-}7\right)$$ $$i.e\ c=+7\ and\ c=-7$$ [A+B=17], when c=+7 $$mean=\ \frac{17+4\left(7\right)}{3}=15$$ when c=-7 $$mean=\ \frac{17+4\left(-7\right)}{3}=\frac{11}{3}$$ ### GMAT/MBA Expert GMAT Instructor Joined 22 Aug 2016 Posted: 2007 messages Followed by: 31 members Upvotes: 470 M7MBA wrote: What is the average (arithmetic mean) of A, B, and 4C? (1) A + B = 17 (2) C^2 = 49 The OA is the option E. Using both statements together is not sufficient to get an answer? Experts, can you show me what is the best way to solve this PS question? You are supposed to calculate the value of (A + B + 4C)/3. Certainly (1) and (2) alone are not sufficient. While (1) does not have the value of C, (2) does not have the value of A and B. Even combining the two statements will not help as C^2 = 49 gives two values of C = 4 and -4. Thus, with each value of C, you get different values of (A + B + 4C)/3. In DS, we want a unique value, which is not the case here. Insufficient. The correct answer: E Hope this helps! -Jay _________________ Manhattan Review GMAT Prep Locations: New York | Jakarta | Nanjing | Berlin | and many more... Schedule your free consultation with an experienced GMAT Prep Advisor! Click here. • 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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