• NEW! FREE Beat The GMAT Quizzes
Hundreds of Questions Highly Detailed Reporting Expert Explanations
• 7 CATs FREE!
If you earn 100 Forum Points

Engage in the Beat The GMAT forums to earn
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 ## Skier Lindsey Vonn completes a straight 300-meter downhill r ##### This topic has 2 expert replies and 1 member reply ### Top Member ## Skier Lindsey Vonn completes a straight 300-meter downhill r ## Timer 00:00 ## Your Answer A B C D E ## Global Stats Difficult Skier Lindsey Vonn completes a straight 300-meter downhill run in t seconds and at an average speed of (x + 10) meters per second. She then rides a chairlift back up the mountain the same distance at an average speed of (x - 8) meters per second. If the ride up the mountain took 135 seconds longer than her run down the mountain, what was her average speed, in meters per second, during her downhill run? (A) 10 (B) 15 (C) 20 (D) 25 (E) 30 OA C Source: Manhattan Prep ### GMAT/MBA Expert GMAT Instructor Joined 25 May 2010 Posted: 15103 messages Followed by: 1859 members Upvotes: 13060 GMAT Score: 790 BTGmoderatorDC wrote: Skier Lindsey Vonn completes a straight 300-meter downhill run in t seconds and at an average speed of (x + 10) meters per second. She then rides a chairlift back up the mountain the same distance at an average speed of (x - 8) meters per second. If the ride up the mountain took 135 seconds longer than her run down the mountain, what was her average speed, in meters per second, during her downhill run? (A) 10 (B) 15 (C) 20 (D) 25 (E) 30 Downhill speed - uphill speed = (x+10) - (x-8) = 18. Implication: The downhill speed is 18 mps greater than the uphill speed. We can PLUG IN THE ANSWERS, which represent the downhill speed. Since the downhill speed is 18 mps greater than the uphill speed, the correct answer must be GREATER THAN 18. Eliminate A and B. The remaining answer choices imply the following: C: downhill speed = 20, uphill speed = 20-18 = 2 D: downhill speed = 25, uphill speed = 25-18 = 7 E: downhill speed = 30, uphill speed = 30-18 = 12 Since the value in red does not divide evenly into the 300-meter distance, D is almost certain to be incorrect. When the correct answer is plugged in, uphill time - downhill time = 135 seconds. C: downhill speed = 20, uphill speed = 20-18 = 2 Time to travel 300 meters uphill at a speed of 2 mps = 300/2 = 150 seconds. Time to travel 300 meters downhill at a speed of 20 mps = 300/20 = 15 seconds. Uphill time - downhill time = 150-15 = 135 seconds. Success! The correct answer is C. _________________ 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 Backsolving is the preferred approach for this one 300/(x-8) - 300/(x+10) = 135 We are asked for the value of x+10 So we can start with C = X+10 = 20 So x = 10 300/2 - 300 / 20 = 135 It Satisfies. Hence answer is C. ### GMAT/MBA Expert GMAT Instructor Joined 25 Apr 2015 Posted: 2012 messages Followed by: 14 members Upvotes: 43 BTGmoderatorDC wrote: Skier Lindsey Vonn completes a straight 300-meter downhill run in t seconds and at an average speed of (x + 10) meters per second. She then rides a chairlift back up the mountain the same distance at an average speed of (x - 8) meters per second. If the ride up the mountain took 135 seconds longer than her run down the mountain, what was her average speed, in meters per second, during her downhill run? (A) 10 (B) 15 (C) 20 (D) 25 (E) 30 OA C Source: Manhattan Prep We can let the time going down = 300/(x +10) and the time going up as 300/(x - 8), thus: 300/(x +10) + 135 = 300/(x - 8) Multiplying by (x + 10)(x - 8), we have: 300(x - 8) + 135(x + 10)(x - 8) = 300(x + 10) 20(x - 8) + 9(x + 10)(x - 8) = 20(x + 10) 20x - 160 + 9(x^2 + 2x - 80) = 20x + 200 20x - 160 + 9x^2 + 18x - 720 = 20x + 200 9x^2 + 18x - 1,080 = 0 x^2 + 2x -120 = 0 (x + 12)(x - 10) = 0 x = -12 or x = 10 Since x can’t be negative, x must be 10. Therefore, the speed for the downhill run was 20 meters per second. Answer: C _________________ Scott Woodbury-Stewart Founder and CEO • 1 Hour Free BEAT THE GMAT EXCLUSIVE 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 • Magoosh Study with Magoosh GMAT prep 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

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 GMAT Exam
Know how you'd score today for \$0

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 Trial & Practice Exam
BEAT THE GMAT EXCLUSIVE

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

### Top First Responders*

1 fskilnik@GMATH 55 first replies
2 GMATGuruNY 52 first replies
3 Brent@GMATPrepNow 51 first replies
4 Jay@ManhattanReview 39 first replies
5 Rich.C@EMPOWERgma... 23 first replies
* Only counts replies to topics started in last 30 days
See More Top Beat The GMAT Members

### Most Active Experts

1 Scott@TargetTestPrep

Target Test Prep

198 posts
2 fskilnik@GMATH

GMATH Teacher

154 posts
3 Brent@GMATPrepNow

GMAT Prep Now Teacher

97 posts
4 Max@Math Revolution

Math Revolution

89 posts
5 GMATGuruNY

The Princeton Review Teacher

76 posts
See More Top Beat The GMAT Experts