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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 ## A car traveling at a certain constant speed... tagged by: BTGmoderatorLU ##### This topic has 3 expert replies and 0 member replies ### Top Member ## A car traveling at a certain constant speed... A car traveling at a certain constant speed takes 5 seconds longer to travel 1 km than it would take to travel 1 km at 80 km/h. At what speed, in km/h, is the car traveling? A. 70 B. 72 C. 74 D. 75 E. 78 The OA is B. I know that 1 kilometer at 80 km/h is covered in a time = 1/80 hours, in seconds will be 3600/80 = 45 seconds. I stuck here. I'm confused by this PS question. Experts, any suggestion about how can I solve it? Thanks in advance. ### GMAT/MBA Expert Elite Legendary Member Joined 23 Jun 2013 Posted: 9955 messages Followed by: 493 members Upvotes: 2867 GMAT Score: 800 Hi LUANDATO, We're told that a car traveling at a certain constant speed takes 5 seconds longer to travel 1 km than it would take to travel 1 km at 80 km/hour. We're asked at what speed, in km/hour, the car is traveling. Your 'first step' - to convert km/hour into seconds/km is perfect. Since there are 3600 seconds per hour, it would take 3600/80 = 45 seconds to travel 1 km when traveling 80km/hour. We're told that it takes 5 seconds LONGER to travel that same distance, so we now have to add those 5 seconds and 'work backwards' to find the speed... (45+5) = 50 seconds to travel 1 km Since there are 3600 seconds per hour, then we would end up traveling 3600/50 = 72 km in one hour. Thus, the speed is 72 km/hour. Final Answer: B GMAT assassins aren't born, they're made, Rich _________________ Contact Rich at Rich.C@empowergmat.com ### GMAT/MBA Expert GMAT Instructor Joined 25 May 2010 Posted: 14945 messages Followed by: 1855 members Upvotes: 13060 GMAT Score: 790 LUANDATO wrote: A car traveling at a certain constant speed takes 5 seconds longer to travel 1 km than it would take to travel 1 km at 80 km/h. At what speed, in km/h, is the car traveling? A. 70 B. 72 C. 74 D. 75 E. 78 80 kilometers per hour = 80 kilometers in 3600 seconds. A car takes 5 seconds longer. Since 1 kilometer takes 5 seconds longer, 80 kilometers takes 400 seconds longer, implying a rate of 80 kilometers in 4000 seconds: (80 kilometers)/(4000 seconds) * (3600 seconds)/(1 hour) = 72 kph. The correct answer is B. _________________ 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. ### GMAT/MBA Expert GMAT Instructor Joined 25 Apr 2015 Posted: 1778 messages Followed by: 14 members Upvotes: 43 LUANDATO wrote: A car traveling at a certain constant speed takes 5 seconds longer to travel 1 km than it would take to travel 1 km at 80 km/h. At what speed, in km/h, is the car traveling? A. 70 B. 72 C. 74 D. 75 E. 78 If a car is traveling at 80 km per hour, then the number of seconds (x) it takes to travel 1 km can be calculated using the following proportion (note that 1 hour = 3,600 seconds): 80/3600 = 1/x 80x = 3600 x = 45 sec Thus, it takes 45 seconds to travel 1 km if the speed is 80 km/h. Since the car actually takes 5 more seconds (i.e., 50 seconds) to travel 1 km, its speed (r) can be calculated using the following proportion: r/3600 = 1/50 50r = 3600 r = 72 km/h Answer: B _________________ Scott Woodbury-Stewart Founder and CEO • 1 Hour Free BEAT THE GMAT EXCLUSIVE 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 • Award-winning private GMAT tutoring Register now and save up to$200

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