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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 ## GMAT Official Guide 2019 During a trip that they ##### This topic has 3 expert replies and 0 member replies ### Top Member ## GMAT Official Guide 2019 During a trip that they ## Timer 00:00 ## Your Answer A B C D E ## Global Stats Difficult During a trip that they took together, Carmen, Juan, Maria, and Rafael drove an average (arithmetic mean) of 80 miles each. Carmen drove 72 miles, Juan drove 78 miles, and Maria drove 83 miles. How many miles did Rafael drive? A. 80 B. 82 C. 85 D. 87 E. 89 ### GMAT/MBA Expert GMAT Instructor Joined 25 Apr 2015 Posted: 2244 messages Followed by: 18 members Upvotes: 43 Top Reply BTGmoderatorDC wrote: During a trip that they took together, Carmen, Juan, Maria, and Rafael drove an average (arithmetic mean) of 80 miles each. Carmen drove 72 miles, Juan drove 78 miles, and Maria drove 83 miles. How many miles did Rafael drive? A. 80 B. 82 C. 85 D. 87 E. 89 We can create the equation: (72 + 78 + 83 + x)/4 = 80 233 + x = 320 x = 87 Alternate Solution: Carmen drove 8 miles under the average, Juan drove 2 miles under the average and Maria drove 3 miles above the average. If we add these up, we get -8 + (-2) + 3 = -7; which means we are 7 miles under the average. Therefore, Rafael must drive 7 miles over the average to keep the average at 80 miles. Thus, Rafael drove 80 + 7 = 87 miles. Answer: D _________________ Scott Woodbury-Stewart Founder and CEO ### GMAT/MBA Expert Elite Legendary Member Joined 23 Jun 2013 Posted: 10112 messages Followed by: 494 members Upvotes: 2867 GMAT Score: 800 Top Reply Hi All, We're told that during a trip that they took together, Carmen, Juan, Maria, and Rafael drove an average (arithmetic mean) of 80 miles each; Carmen drove 72 miles, Juan drove 78 miles, and Maria drove 83 miles. We're asked how many miles Rafael drove. This question can be solved in a number of different ways; using the Average Formula (as Brent did) is arguably the easiest. You can also use the 'differences' between the three given values and the average to calculate the difference between the fourth value and the average. With an average of 80.... Carmen drove 8 miles LESS than the average Juan drove 2 miles LESS than the average Maria drove 3 miles MORE than the average The 'net effect' of those differences is (-8) + (-2) + (+3) = -7... meaning that the total of those 3 values is 7 LESS than the average. This means that Rafael has to drive far enough to 'offset' that difference. Thus, Rafael drove 7 MORE than the average (re: 80+7 = 87 miles). 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 08 Dec 2008 Posted: 12744 messages Followed by: 1247 members Upvotes: 5254 GMAT Score: 770 BTGmoderatorDC wrote: During a trip that they took together, Carmen, Juan, Maria, and Rafael drove an average (arithmetic mean) of 80 miles each. Carmen drove 72 miles, Juan drove 78 miles, and Maria drove 83 miles. How many miles did Rafael drive? A. 80 B. 82 C. 85 D. 87 E. 89 Let x = the number of miles Rafael drove Average = 80 So, (72 + 78 + 83 + x)/4 = 80 Multiply both sides by 4 to get: 72 + 78 + 83 + x = 320 Simplify: 233 + x = 320 Solve: x = 87 Answer: D 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! • 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 • 5 Day FREE Trial Study Smarter, Not Harder Available with Beat the GMAT members only code • Award-winning private GMAT tutoring Register now and save up to$200

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