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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 Q.65 Problem Solving GMAT Review 13th Edition tagged by: Brent@GMATPrepNow This topic has 3 expert replies and 1 member reply Q.65 Problem Solving GMAT Review 13th Edition Timer 00:00 Your Answer A B C D E Global Stats Difficult The average distance between the Sun and a certain planet is approximately 23*10^14 inches. Which of the following is closest to the average distance between the Sun and the planet, in kilometres? (1 Kilometre is approximately 3.9*10^4 inches) A) 7.1*10^8 B) 5.9*10^9 C) 1.6*10^10 D) 1.6*10^11 E) 5.9*10^11 Answer is B. As per the OG answer description, it took the approximate value of 23/39 as 2/4 and derived at a value of 5*10^9.But, what will be the answer if the approximate value of 23/39 will be taken as 2/3? GMAT/MBA Expert GMAT Instructor Joined 25 May 2010 Posted: 15107 messages Followed by: 1859 members Upvotes: 13060 GMAT Score: 790 The prompt as posted has a typo. It should read as follows: Quote: The average distance between the Sun and a certain planet is approximately 2.3 X 10^14 inches. Which of the following is closest to the average distance between the Sun and the planet, in kilometers? (1 kilometer is approximately 3.9 X 10^4 inches.) (A) 7.1 X 10^8 (B) 5.9 X 10^9 (C) 1.6 X 10^10 (D) 1.6 X 10^11 (E) 5.9 X 10^11 As for your question: Priyaranjan wrote: what will be the answer if the approximate value of 23/39 will be taken as 2/3? (2.3 * 10¹⁴)/(3.9 * 10⁴) ≈ 2/3 * 10¹⁰ ≈ 0.66 * 10¹⁰ = 6.6 * 10⁹. The closest answer choice is B. _________________ 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. GMAT/MBA Expert GMAT Instructor Joined 08 Dec 2008 Posted: 12667 messages Followed by: 1246 members Upvotes: 5254 GMAT Score: 770 Priyaranjan wrote: The average distance between the Sun and a certain planet is approximately 23*10^14 inches. Which of the following is closest to the average distance between the Sun and the planet, in kilometres? (1 Kilometre is approximately 3.9*10^4 inches) A) 7.1 x 10^8 B) 5.9 x 10^9 C) 1.6 x 10^10 D) 1.6 x 10^11 E) 5.9 x 10^11 We can solve the question using equivalent ratios. We're comparing kilometers and inches, so the ratio is kilometers/inches 1 Kilometre is approximately 3.9 x 10^4 inches So, we have the ratio: 1/(3.9 x 10^4) We're told the number of inches to the sun (2.3 X 10^14) and we must find the number of equivalent kilometers. Let d = the number of kilometers. So, we have the ratio: 1/(2.3 X 10^14) We can now write: 1/(3.9 x 10^4) = d/(2.3 X 10^14) To solve for d, first cross multiply to get: d(3.9 x 10^4) = 1(2.3 X 10^14) Solve for d to get: d = (2.3 X 10^14)/(3.9 x 10^4) d = [2.3/3.9][(10^14)/(10^4)] d = [0.59][10^10] Check the answer choices...not there. To get our response into the proper format, rewrite 0.59 as 5.9 x 10^-1 to get... d = [5.9 x 10^-1][10^10] d = 5.9 x 10^9 Answer: B Cheers, Brent _________________ Brent Hanneson – 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 GMAT’s FREE 60-Day Study Guide and reach your target score in 2 months! Senior | Next Rank: 100 Posts Joined 16 Dec 2009 Posted: 37 messages Upvotes: 9 Test Date: November 2009 GMAT Score: 780 Priyaranjan wrote: The average distance between the Sun and a certain planet is approximately 23*10^14 inches. Which of the following is closest to the average distance between the Sun and the planet, in kilometres? (1 Kilometre is approximately 3.9*10^4 inches) A) 7.1*10^8 B) 5.9*10^9 C) 1.6*10^10 D) 1.6*10^11 E) 5.9*10^11 Answer is B. As per the OG answer description, it took the approximate value of 23/39 as 2/4 and derived at a value of 5*10^9.But, what will be the answer if the approximate value of 23/39 will be taken as 2/3? Priyaranjan, Part 1: It's fine to take the approximation as 2/4, provided you keep in mind that it's less than 23/39. Also fine to estimate at 2/3, keeping in mind that it's more than 23/39. An estimate can be paired with a direction to improve eliminations, so this is a good habit to practice. Part 2: Assuming the estimate 2/3, the result as 6.6x10^9, and this is greater than the true value. Regards, Mike www.google.com/+MikeMiagi _________________ www.gmatdojo.com Mindfulness, Concentration, Insight GMAT/MBA Expert GMAT Instructor Joined 25 Apr 2015 Posted: 2012 messages Followed by: 15 members Upvotes: 43 Priyaranjan wrote: The average distance between the Sun and a certain planet is approximately 23*10^14 inches. Which of the following is closest to the average distance between the Sun and the planet, in kilometres? (1 Kilometre is approximately 3.9*10^4 inches) A) 7.1*10^8 B) 5.9*10^9 C) 1.6*10^10 D) 1.6*10^11 E) 5.9*10^11 Answer is B. As per the OG answer description, it took the approximate value of 23/39 as 2/4 and derived at a value of 5*10^9.But, what will be the answer if the approximate value of 23/39 will be taken as 2/3? Solution: This problem is a unit conversion with an added twist of scientific notation. We need to convert 2.3 x 10^14 inches to KILOMETERS. We are given that 1 kilometer is approximately 3.9 X 10^4 inches. We also should recognize that we are being asked which of the following is CLOSEST to the average distance between the Sun and the planet, in kilometers. Because we are being asked for an approximation, we can use some estimation here. To convert 2.3 x 10^14 inches to kilometers, we need to multiply 2.3 x 10^14 inches by the ratio of: 1 km/(3.9 x 10^4 inches) However, before doing this multiplication, it will make things easier by “cleaning up” each scientific notation expression. Let’s start with 2.3 x 10^14 inches. 2.3 x 10^14 inches is equivalent to 23 x 10^13 inches Notice that because we turn 2.3 into 23, or move the decimal one place to the right, we have to then turn 10^14 into 10^13, or move the decimal one place to the LEFT to counterbalance the fact that we’ve moved the decimal one place to the right for 2.3. Next we can adjust 3.9 x 10^4 inches. However, we can simply round this value up to 4 x 10^4 inches because the question only asks for the closest answer. Since we’ve rounded 3.9 up to 4, let’s round 23 up to 24 also. That is, we are converting 24 x 10^13 inches into kilometers given that 1 km is approximately 4 x 10^4 inches: (24 x 10^13 inches) x 1 km/(4 x 10^4 inches) (24 x 10^13)/(4 x 10^4) km We can break this work up into two separate calculations: 1) 24/4 = 6 2) 10^13/10^4 = 10^9 Thus, our answer is about 6 x 10^9 km. We see that the closest answer is 5.9 x 10^9. Answer: B _________________ Scott Woodbury-Stewart Founder and CEO • 5 Day FREE Trial Study Smarter, Not Harder 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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