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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 surface area of a sphere is 4Ï€R^2, and the... tagged by: BTGmoderatorLU ##### This topic has 2 expert replies and 0 member replies ### Top Member ## The surface area of a sphere is 4Ï€R^2, and the... The surface area of a sphere is 4Ï€R^2, and the volume of a sphere is (4/3)Â·Ï€Â·R^3, where R is the radius of the sphere. If the volume of a certain sphere is double the surface area of that sphere, what is the radius of that certain sphere? A. 1.5 B. 6/Ï€ C. 1.5Ï€ D. 6 E. 6Ï€ The OA is D. Please, can any expert assist me with this PS question? I'm really confused with it, how can I solve it? Thanks in advanced. ### GMAT/MBA Expert Elite Legendary Member Joined 23 Jun 2013 Posted: 10197 messages Followed by: 497 members Upvotes: 2867 GMAT Score: 800 Hi LUANDATO, While this question might 'look scary', you can actually just set up one equation and simplify it to get the correct answer: We're given a few facts to work with: 1) The surface area of a sphere is 4Ï€R^2 2) The volume of a sphere is (4/3)Â·Ï€Â·R^3 3) The volume of a certain sphere is DOUBLE the surface area of that sphere We're asked for the radius (R) of that sphere. The equation we can set up is... (4/3)(Ï€)(R^3) = (2)(4)(Ï€)(R^2) (4/3)(R) = 8 R = (8)(3/4) R = 24/4 = 6 Final Answer: D GMAT assassins aren't born, they're made, Rich _________________ Contact Rich at Rich.C@empowergmat.com ### GMAT/MBA Expert GMAT Instructor Joined 04 Oct 2017 Posted: 551 messages Followed by: 11 members Upvotes: 180 Quote: The surface area of a sphere is 4Ï€R^2, and the volume of a sphere is (4/3)Â·Ï€Â·R^3, where R is the radius of the sphere. If the volume of a certain sphere is double the surface area of that sphere, what is the radius of that certain sphere? A. 1.5 B. 6/Ï€ C. 1.5Ï€ D. 6 E. 6Ï€ The OA is D. Please, can any expert assist me with this PS question? I'm really confused with it, how can I solve it? Thanks in advanced. Hi LUANDATO, Let's take a look at your question. $$Area=\ 4\pi R^2$$ $$Volume=\frac{4}{3}\pi R^3$$ The question states: "If the volume of a certain sphere is double the surface area of that sphere", we can write it as: $$Volume=2\times Area$$ $$\frac{4}{3}\pi R^3=2\times\left(4\pi R^2\right)$$ $$\frac{1}{3}\pi R=2\times\left(\pi\right)$$ $$\frac{1}{3}R=2$$ $$R=2\times3$$ $$R=6$$ Therefore, radius of the sphere is 6. Hence, Option D is correct. Hope it helps. I am available if you'd like any follow up. _________________ GMAT Prep From The Economist We offer 70+ point score improvement money back guarantee. Our average student improves 98 points. Free 7-Day Test Prep with Economist GMAT Tutor - Receive free access to the top-rated GMAT prep course including a 1-on-1 strategy session, 2 full-length tests, and 5 ask-a-tutor messages. Get started now. • Free Veritas GMAT Class Experience Lesson 1 Live Free 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 • Free Trial & Practice Exam BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • FREE GMAT Exam Know how you'd score today for$0

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