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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 ## Train,Train,Train! ##### This topic has 1 expert reply and 1 member reply ## Train,Train,Train! Stations X and Y are connected by two separate, straight, parallel rail lines that are 250 miles long. Train P and train Q simultaneously left Station X and Station Y, respectively, and each train traveled to the other's point of departure. The two trains passed each other after traveling for 2 hours. When the two trains passed, which train was nearer to its destination? (1)At the time when the two trains passed, train P had averaged a speed of 70 miles per hour. (2)Train Q averaged a speed of 55 miles per hour for the entire trip. GMAT Instructor Joined 01 May 2008 Posted: 189 messages Followed by: 1 members Upvotes: 25 Test Date: 2/18/2006 GMAT Score: 750+ Statement 1 tells us that train P had traveled at an average speed of 70 mph until the trains crossed, and we know it has traveled for 2 hours when the trains cross. Thus, it had traveled: d =r*t d=70(m/h)*2h=140 mi Since we know station X and Y are 250 miles apart, we know that the trains meet at a point that is 140 mi from station X (where P left), and 110 miles from station Y (where Q left). We thus know that train P is closer to its destination, and we have sufficient information from statement 1. Statement 2 tells us that train Q had traveled at an average speed of 55 mph for the whole trip. However, we don't know what its average was at the point the trains met, and thus we can't figure out how far it had traveled when they met. Thus, statement 2 is insufficient. Since statement 1 is sufficient and statement 2 is not, the answer is A. _________________ Tatiana Becker | GMAT Instructor | Veritas Prep Last edited by VP_Tatiana on Sun Jul 20, 2008 2:08 pm; edited 2 times in total ### GMAT/MBA Expert GMAT Instructor Joined 08 Jan 2008 Posted: 3225 messages Followed by: 611 members Upvotes: 1710 GMAT Score: 800 zagcollins wrote: Stations X and Y are connected by two separate, straight, parallel rail lines that are 250 miles long. Train P and train Q simultaneously left Station X and Station Y, respectively, and each train traveled to the other's point of departure. The two trains passed each other after traveling for 2 hours. When the two trains passed, which train was nearer to its destination? (1)At the time when the two trains passed, train P had averaged a speed of 70 miles per hour. (2)Train Q averaged a speed of 55 miles per hour for the entire trip. Let's try answering this with a lot less math, which should always be your goal in data sufficiency. Remember, we don't care what the answer is, we just care if we can get an answer! Let's start by really understanding the question. We know the distance and we know at what time the trains pass each other. In order to determine which one is closer to its destination, we need to know their relative speeds (we don't even need to know their actual speeds - just knowing that one is moving faster than the other would be sufficient). (1) Gives us the speed of P up until the trains met. Well, we can certainly figure out exactly where train P would be (and since it's where they pass, we know where Q would be as well) if we know P's time and rate, so we could see which one is closer to the end of the trip: sufficient. (2) This statement is kind of nasty! Just because train Q averaged 55mph for the entire trip, we can't assume that train Q was moving at a constant speed. For all we know, train Q traveled part of the trip at 80mph and another part at 30mph. Since we don't know how quickly Q was traveling for the first part of the journey (i.e. until they met), we have no way of calculating how close the two trains were to their destinations: insufficient. (1) is suff and (2) isn't: choose (A). Free GMAT Practice Test under Proctored Conditions! - Find a practice test near you or live and online in Kaplan's Classroom Anywhere environment. Register today! • Free Trial & Practice Exam BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Get 300+ Practice Questions 25 Video lessons and 6 Webinars for FREE Available with Beat the GMAT members only code • Free Practice Test & Review How would you score if you took the GMAT 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 • Award-winning private GMAT tutoring Register now and save up to$200

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