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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 ## On a certain Monday, Carlos drove to work at an average tagged by: BTGmoderatorLU ##### This topic has 3 expert replies and 1 member reply ### Top Member ## On a certain Monday, Carlos drove to work at an average ## Timer 00:00 ## Your Answer A B C D E ## Global Stats Difficult Source: Veritas Prep On a certain Monday, Carlos drove to work at an average speed of 50 miles per hour and home from work along exactly the same route at an average speed of 70 miles per hour. Which of the following is closest to his average speed for both trips combined? A. 58.3 miles per hour B. 60.0 miles per hour C. 62.6 miles per hour D. 65.4 miles per hour E. It cannot be determined from the information given The OA is A ### GMAT/MBA Expert GMAT Instructor Joined 08 Dec 2008 Posted: 12655 messages Followed by: 1245 members Upvotes: 5254 GMAT Score: 770 BTGmoderatorLU wrote: Source: Veritas Prep On a certain Monday, Carlos drove to work at an average speed of 50 miles per hour and home from work along exactly the same route at an average speed of 70 miles per hour. Which of the following is closest to his average speed for both trips combined? A. 58.3 miles per hour B. 60.0 miles per hour C. 62.6 miles per hour D. 65.4 miles per hour E. It cannot be determined from the information given The OA is A [size=150]Average speed = (TOTAL distance)/TOTAL travel time)[/size] Let d = the distance from work to home Carlos drove to work at an average speed of 50 miles per hour Time = distance/speed So, travel time TO work = d/50 hours Carlos drove home from work at an average speed of 70 miles per hour So, travel time FROM work = d/70 hours So, TOTAL travel time = d/50 + d/70 = 7d/350 + 5d/350 [rewrite with common denominators] = 12d/350 Also, TOTAL distance = d + d = 2d Which of the following is closest to his average speed for both trips combined? Average speed = (TOTAL distance)/TOTAL travel time) = (2d)/(12d/350) = (2d)(350/12d) = 700d/12d = 700/12 = 350/6 STOP. Since 360/60 = 60, we know that 350/6 will be LESS THAN 60 Answer: A 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! ### GMAT/MBA Expert GMAT Instructor Joined 25 May 2010 Posted: 15103 messages Followed by: 1859 members Upvotes: 13060 GMAT Score: 790 BTGmoderatorLU wrote: Source: Veritas Prep On a certain Monday, Carlos drove to work at an average speed of 50 miles per hour and home from work along exactly the same route at an average speed of 70 miles per hour. Which of the following is closest to his average speed for both trips combined? A. 58.3 miles per hour B. 60.0 miles per hour C. 62.6 miles per hour D. 65.4 miles per hour E. It cannot be determined from the information given When the SAME DISTANCE is traveled at two different speeds, the average speed for the entire trip will be CLOSER TO THE LOWER SPEED than to the higher speed. The reason: The portion traveled at the lower speed takes LONGER. Since more time is spent at the lower speed than at the higher speed, the average speed for the entire trip will be closer to the lower speed. Here, halfway between the two speeds = the average of the two speeds = (50+70)/2 = 60. To be closer to the lower speed and to the higher speed, the average speed for the entire trip must be LESS THAN 60. The correct answer is A. _________________ 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. ### Top Member Legendary Member Joined 29 Oct 2017 Posted: 781 messages Followed by: 4 members For these type of questions we can apply direct formula given below: 2ab/(a+b), where a & b are avg. speed. So 2x50x70/(120)= 58.33 (approx). ### GMAT/MBA Expert GMAT Instructor Joined 25 Apr 2015 Posted: 2012 messages Followed by: 14 members Upvotes: 43 BTGmoderatorLU wrote: Source: Veritas Prep On a certain Monday, Carlos drove to work at an average speed of 50 miles per hour and home from work along exactly the same route at an average speed of 70 miles per hour. Which of the following is closest to his average speed for both trips combined? A. 58.3 miles per hour B. 60.0 miles per hour C. 62.6 miles per hour D. 65.4 miles per hour E. It cannot be determined from the information given We can use the following formula: average rate = total distance/total time If we let the distance each way = d, then the time to work = d/50, and the time from work = d/70. Thus: average rate = 2d/(d/50 + d/70) average rate = 2d/(7d/350 + 5d/350) average rate = 2d/(12d/350) average rate = (2d x 350)/12d average rate = 350/6 = 58.3 mph Answer: A _________________ Scott Woodbury-Stewart Founder and CEO • 5 Day FREE Trial Study Smarter, Not Harder Available with Beat the GMAT members only code • 1 Hour Free 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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