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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 ## Drill Press M can bore 3000 holes an hour and Drill Press... tagged by: BTGmoderatorLU ##### This topic has 2 expert replies and 0 member replies ### Top Member ## Drill Press M can bore 3000 holes an hour and Drill Press... Drill Press M can bore 3000 holes an hour and Drill Press N can bore 2500 holes an hour. If the two machines together must bore 45,000 holes, and if each machine can operate for at most 9 hours, what is the least amount of time, in hours, Drill Press N must operate? A. 6 B. 7 C. 36/7 D. 8 E. 90/11 The OA is C. I'm really confused by this PS question. Experts, any suggestion about how to solve it? Thanks in advance. ### GMAT/MBA Expert GMAT Instructor Joined 04 Oct 2017 Posted: 551 messages Followed by: 11 members Upvotes: 180 Top Reply LUANDATO wrote: Drill Press M can bore 3000 holes an hour and Drill Press N can bore 2500 holes an hour. If the two machines together must bore 45,000 holes, and if each machine can operate for at most 9 hours, what is the least amount of time, in hours, Drill Press N must operate? A. 6 B. 7 C. 36/7 D. 8 E. 90/11 The OA is C. I'm really confused by this PS question. Experts, any suggestion about how to solve it? Thanks in advance. Hello LUANDATO. There is a mistake with the option C. The correct answer should be 36/5. Let's see why. We know that Drill Press M has to operate for 9 hours (in this way, the number of hours that has to operate Drill Press N will be minimum). Hence, Drill Press M will bore 3000*9 = 27.000 holes. Now, Drill Press N has to bore 45.000-27.000 = 18.000 holes. The time that Drill Press N has to operate is 18.000 / 2.500 = 180 / 25 = 36/5 hours. This is why the correct answer is 36/5 hours. I hope this explanation may help you. Feel free to ask me again if you have a doubt. Regards. _________________ 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. ### GMAT/MBA Expert GMAT Instructor Joined 25 Apr 2015 Posted: 2950 messages Followed by: 19 members Upvotes: 43 BTGmoderatorLU wrote: Drill Press M can bore 3000 holes an hour and Drill Press N can bore 2500 holes an hour. If the two machines together must bore 45,000 holes, and if each machine can operate for at most 9 hours, what is the least amount of time, in hours, Drill Press N must operate? A. 6 B. 7 C. 36/7 D. 8 E. 90/11 We are given that the rate of Drill Press M is 3000 holes/hour and the rate of Drill Press N is 2500 holes/hour. Since each machine can operate for at most 9 hours and we need to determine the minimum number of hours of operating time for N, we can let M work for 9 hours, and thus 3000 x 9 = 27,000 holes are completed, leaving 45,000 - 27,000 = 18,000 holes to be completed by N. Since time = work/rate, N must operate for 18,000/2,500 = 180/25 = 36/5 hours. (Note the typo for choice C, which should be 36/5.) Answer: C _________________ Scott Woodbury-Stewart Founder and CEO scott@targettestprep.com See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews • Magoosh Study with Magoosh GMAT prep Available with Beat the GMAT members only code • FREE GMAT Exam Know how you'd score today for$0

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