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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 ## Work/Rate problem tagged by: BTGmoderatorRO ##### This topic has 2 expert replies and 0 member replies ## Work/Rate problem An automobile tire has two punctures. The first puncture by itself would make the tire flat in 9 minutes. The second puncture by itself would make the tire flat in 6 minutes. How long will it take for both punctures together to make the tire flat? (Assume the air leaks out at a constant rate.) (A) 18/5 minutes (B) 4 minutes (C) 21/4 minutes (D) 15/2 minutes (E) 15 minutes OA is a which formula will i use here to get the correct answer to this question? can any expert help me here? Thank you ### GMAT/MBA Expert GMAT Instructor Joined 04 Oct 2017 Posted: 551 messages Followed by: 11 members Upvotes: 180 Quote: An automobile tire has two punctures. The first puncture by itself would make the tire flat in 9 minutes. The second puncture by itself would make the tire flat in 6 minutes. How long will it take for both punctures together to make the tire flat? (Assume the air leaks out at a constant rate.) (A) 18/5 minutes (B) 4 minutes (C) 21/4 minutes (D) 15/2 minutes (E) 15 minutes OA is a which formula will i use here to get the correct answer to this question? can any expert help me here? Thank you Hi Roland2rule, Let's take a look at your question. The questions states that: "The first puncture by itself would make the tire flat in 9 minutes. The second puncture by itself would make the tire flat in 6 minutes." In one minute, the part of the tire made flat by the first puncture = 1/9 In one minute, the part of the tire made flat by the second puncture = 1/6 Now we can find out the part of the tire made flat by both the punctures in one minute by just adding them up. In one minute, the part of the tire made flat by both the punctures = $$=\frac{1}{9}+\frac{1}{6}$$ $$=\frac{2+3}{18}$$ $$=\frac{5}{18}$$ Reading it in reverse order, we can now say that both the punctures together will make the tire flat in 18/5 minutes. Therefore, Option A 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. ### GMAT/MBA Expert Elite Legendary Member Joined 23 Jun 2013 Posted: 10197 messages Followed by: 497 members Upvotes: 2867 GMAT Score: 800 Hi Roland2rule, This is an example of a "Work Formula" question - when you have two entities working together on a task, you can use the following formula to determine how long it will take the two entities to complete the task: (A)(B)/(A+B) = time to complete the task (where A and B are the two times it takes the individuals to complete the task when working alone) We're told that the first puncture would create a flat tire in 9 minutes and the second puncture would make a flat tire in 6 minutes. Plugging in those values, we'd have... (9)(6)/(9+6) = 54/15 = 18/5 = 3 3/5 minutes to make a flat tire Final Answer: A GMAT assassins aren't born, they're made, Rich _________________ Contact Rich at Rich.C@empowergmat.com • Free Practice Test & Review How would you score if you took the GMAT Available with Beat the GMAT members only code • 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 • 5-Day Free Trial 5-day free, full-access trial TTP Quant Available with Beat the GMAT members only code • FREE GMAT Exam Know how you'd score today for$0

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