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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 line k in the xy-coordinate plane has the equation Ax + B ##### This topic has 2 expert replies and 0 member replies ### Top Member ## If line k in the xy-coordinate plane has the equation Ax + B ## Timer 00:00 ## Your Answer A B C D E ## Global Stats Difficult If line k in the xy-coordinate plane has the equation Ax + By = C, what is the slope of line k ? (1) A = 2B (2) C = 4B OA A Source: Magoosh ### GMAT/MBA Expert GMAT Instructor Joined 08 Dec 2008 Posted: 12412 messages Followed by: 1244 members Upvotes: 5254 GMAT Score: 770 BTGmoderatorDC wrote: If line k in the xy-coordinate plane has the equation Ax + By = C, what is the slope of line k ? (1) A = 2B (2) C = 4B Given: Line k has the equation Ax + By = C Target question: What is the slope of line k ? This is a good candidate for rephrasing the target question. Let's take the given equation Ax + By = C and rewrite it in slope y-intercept form, y = mx + b, where m = slope and b = y-intercept GIVEN: Ax + By = C Subtract Ax from both sides to get: By = -Ax + C Divide both sides by B to get: y = -Ax/B + C/B Rewrite to get: y = (-A/B)x + C/B With the line's equation written in this form, we can see that line k has slope -A/B and y-intercept C/B So, we can REPHRASE our target question.... REPHRASED target question: What is the value of -A/B ? Aside: Hereâ€™s a video with tips on rephrasing the target question: http://www.gmatprepnow.com/module/gmat-data-sufficiency?id=1100 Statement 1: A = 2B Divide both sides by B to get: A/B = 2 This means -A/B = -2 So, the answer to the REPHRASED target question is -A/B = -2 Since we can answer the REPHRASED target question with certainty, statement 1 is SUFFICIENT Statement 2: C = 4B Since we have no information about A, there's no way to determine the value of -A/B Since we cannot answer the REPHRASED target question with certainty, statement 2 is NOT SUFFICIENT Answer: A 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 09 Oct 2010 Posted: 964 messages Followed by: 27 members Upvotes: 59 BTGmoderatorDC wrote: If line k in the xy-coordinate plane has the equation Ax + By = C, what is the slope of line k ? (1) A = 2B (2) C = 4B Source: Magoosh Important: from the stem we know (implicitly) that line k HAS a slope, i.e., line k is non-vertical, i.e., B is nonzero. $$Ax + By = C\,\,\,\,\,\mathop \Leftrightarrow \limits^{B\,\, \ne \,\,0} \,\,\,y\,\, = - {A \over B}\left( x \right)\,\, + \,\,{C \over A}$$ $$? = - {A \over B}$$ $$\left( 1 \right)\,\,\,A = 2B\,\,\,\,\mathop \Rightarrow \limits^{B\,\, \ne \,\,0} \,\,\,\,\,? = - {A \over B} = - 2\,\,\,\,\,\, \Rightarrow \,\,\,\,\,\,{\rm{SUFF}}.$$ $$\left( 2 \right)\,\,\,C = 4B\,\,\,\left\{ \matrix{ \,{\rm{Take}}\,\,\left( {A,B,C} \right) = \left( {1,1,4} \right)\,\,\,\,\, \Rightarrow \,\,\,\,\,\,{\rm{?}}\,\,\,{\rm{ = }}\,\, - 1\,\, \hfill \cr \,{\rm{Take}}\,\,\left( {A,B,C} \right) = \left( {2,1,4} \right)\,\,\,\,\, \Rightarrow \,\,\,\,\,\,{\rm{?}}\,\,\,{\rm{ = }}\,\, - 2\,\, \hfill \cr} \right.\,\,\,\,\,\,\, \Rightarrow \,\,\,\,\,\,{\rm{INSUFF}}.$$ This solution follows the notations and rationale taught in the GMATH method. Regards, Fabio. _________________ Fabio Skilnik :: https://GMATH.net (Math for the GMAT) or https://GMATH.com.br (Portuguese version) Course release PROMO : finish our test drive till 30/Dec with (at least) 50 correct answers out of 92 (12-questions Mock included) to gain a 50% discount! • Free Trial & Practice Exam BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Free Practice Test & Review How would you score if you took the GMAT Available with Beat the GMAT members only code • 5-Day Free Trial 5-day free, full-access trial TTP Quant Available with Beat the GMAT members only code • Get 300+ Practice Questions 25 Video lessons and 6 Webinars for 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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