December 10, 2018 December 10, 2018 10:00 PM PST 11:00 PM PST Practice the one most important Quant section  Integer properties, and rapidly improve your skills. December 11, 2018 December 11, 2018 09:00 PM EST 10:00 PM EST Strategies and techniques for approaching featured GMAT topics. December 11 at 9 PM EST.
Author 
Message 
TAGS:

Hide Tags

Intern
Joined: 19 Sep 2014
Posts: 21
Concentration: Finance, Economics
GMAT Date: 05052015

In the figure above, car A and car B simultaneously begin travelling..
[#permalink]
Show Tags
Updated on: 04 Feb 2015, 01:02
Question Stats:
58% (02:01) correct 42% (02:23) wrong based on 357 sessions
HideShow timer Statistics
Attachment:
DS car question.jpg [ 7.59 KiB  Viewed 5021 times ]
In the figure above, car A and car B simultaneously begin travelling around a circular park with area of \(4\pi\) square miles. Both cars start form the same point, the START location shown in the figure, and travel with constant speed rates until they meet. Car A travels counterclockwise and car B travels clockwise. Where along the track will they meet? ( Note: figure not drawn to scale). (1) Car B travels 30 mph faster than car A. (2) Car A travels twice as slowly as car B. Could someone pleas explain the answer to this question. It will be much appreciated, thank you
Official Answer and Stats are available only to registered users. Register/ Login.
Originally posted by kdatt1991 on 03 Feb 2015, 17:40.
Last edited by Bunuel on 04 Feb 2015, 01:02, edited 1 time in total.
Edited the question.



Manager
Joined: 14 Sep 2014
Posts: 105
Concentration: Technology, Finance
WE: Analyst (Other)

Re: In the figure above, car A and car B simultaneously begin travelling..
[#permalink]
Show Tags
03 Feb 2015, 18:11
The key to this problem is understanding that the only information you need is the ratio of speeds. You don't need to solve for the actual answer, so the area and exact speeds are irrelevant.
Statement 1: This is insufficient. Let's consider two scenarios and image a different circular park with a circumference of 100m. If car A travels 10 mph, then car B travels 40 mph. In 2 hours, car B will have traveled 80% of the circumference when it intercepts car A. If car A travels 30 mph, then car B travels 60 mph. In a little over an hour, car B will have traveled about 60% of the distance when it intercepts car A.
Statement 2: This is sufficient. Regardless of the actual speeds, car A and B will meet at one place. In the time it takes car B to travel 2/3 of the distance, car A has traveled 1/3 of the distance. Together, they have covered the entire circumference of the park.



Math Expert
Joined: 02 Sep 2009
Posts: 51072

In the figure above, car A and car B simultaneously begin traveling ar
[#permalink]
Show Tags
16 Jul 2015, 00:26



CEO
Joined: 20 Mar 2014
Posts: 2633
Concentration: Finance, Strategy
GPA: 3.7
WE: Engineering (Aerospace and Defense)

Re: In the figure above, car A and car B simultaneously begin traveling ar
[#permalink]
Show Tags
16 Jul 2015, 02:40
Bunuel wrote: In the figure above, car A and car B simultaneously begin traveling around a circular park with area of 4π square miles. Both cars start from the same point, the START location shown in the figure and travel with constant speed rates until they meet. Car A travels counterclockwise and car B travels clockwise. Where along the track will they meet? (1) Car B travels 30 mph faster than car A. (2) Car A travels twice slower than car B. Kudos for a correct solution.Attachment: Picture_circle.png Given: area of the circle = \(4\pi\) > radius of the circle = 2> circumference of the circle = \(4\pi\) Let Va and Vb be the speeds of A and B respectively. For 'where' do they meet, we have the following equation : \(Va*T+Vb*T =4\pi\)  (1), where T is the time after which they both meet. Per the question, Va.T = ? or Vb.T = ? Per statement 1, Vb = Va+30. This is not sufficient as this equation with 1 leaves us with 2 equations and 3 variables (Va , Vb, T) We can not isolate Vb.T or Va.T from this. Thus this statement is not sufficient. Per statement 2, Va = Vb /2 (twice slower = half the speed). Susbstituting this in equation (1) we get, \(Vb*T = 8\pi / 3\) . Thus this statement is sufficient. Hence B is the correct answer.



CEO
Status: GMATINSIGHT Tutor
Joined: 08 Jul 2010
Posts: 2710
Location: India
GMAT: INSIGHT
WE: Education (Education)

Re: In the figure above, car A and car B simultaneously begin traveling ar
[#permalink]
Show Tags
16 Jul 2015, 09:57
Bunuel wrote: In the figure above, car A and car B simultaneously begin traveling around a circular park with area of 4π square miles. Both cars start from the same point, the START location shown in the figure and travel with constant speed rates until they meet. Car A travels counterclockwise and car B travels clockwise. Where along the track will they meet? (1) Car B travels 30 mph faster than car A. (2) Car A travels twice slower than car B. Kudos for a correct solution.Attachment: Picture_circle.png From the property of Speed, Distance and Time For Constant Time Speed of A / Speed of B = Distance travelled by A / Distance travelled by B
Area of Track = 4π square miles = π*r^2 square miles i.e. radius = 2 We have the length of Track = 2*π*r miles = 4π So we only require the ratio of speeds to find the ratio of Distance travelled by them and find their meeting pointQuestion : Distance of Meeting point along the track = ?Statement 1: Car B travels 30 mph faster than car A.This statement provides the difference of speeds but not the ratio of speeds. Therefore, NOT SUFFICIENTStatement 2: Car A travels twice slower than car B.i.e. Speed of B = 2* Speed of A Ratio of speeds is 2/1 i.e. Ratio of distance covered till they meet = 2:1 i.e. Meeting Point = (2/3)4π = (8/3)π (in Clockwise direction) SUFFICIENTAnswer: Option B
_________________
Prosper!!! GMATinsight Bhoopendra Singh and Dr.Sushma Jha email: info@GMATinsight.com I Call us : +919999687183 / 9891333772 Online OneonOne Skype based classes and Classroom Coaching in South and West Delhi http://www.GMATinsight.com/testimonials.html
ACCESS FREE GMAT TESTS HERE:22 ONLINE FREE (FULL LENGTH) GMAT CAT (PRACTICE TESTS) LINK COLLECTION



Math Expert
Joined: 02 Sep 2009
Posts: 51072

Re: In the figure above, car A and car B simultaneously begin traveling ar
[#permalink]
Show Tags
19 Jul 2015, 12:32
Bunuel wrote: In the figure above, car A and car B simultaneously begin traveling around a circular park with area of 4π square miles. Both cars start from the same point, the START location shown in the figure and travel with constant speed rates until they meet. Car A travels counterclockwise and car B travels clockwise. Where along the track will they meet? (1) Car B travels 30 mph faster than car A. (2) Car A travels twice slower than car B. Kudos for a correct solution.Attachment: Picture_circle.png 800score Official Solution:Knowing the area of the park, we can find its radius (πr² = 4π square miles, so r = 2 miles). Knowing the radius, we can find the length of the road (the circumference, it equals 2πr = 4π miles). To visualize this question, think about a circle as just a line segment joined at its two ends. Let’s first cut the circle at the starting point and make it into a straight line. Notice that cars A and B are at opposite ends of the line traveling toward each other. A [ ______________________ ] B Let’s denote the speed rate of car A by x mph and the speed rate of car B by y mph. When they meet, the whole distance will be the sum of the paths they have travelled. Since they’ve started simultaneously, then they both travelled for the same time. Let’s denote it by t hours. This gives us the following relation: x × t + y × t = 4π Statement (1) gives us the fact that y = x + 30. The relation transforms into xt + (x + 30)t = 4π. Let’s plug two values to see if we get different results. If x = 5, then t = π/10. So the cars would travel 5π/10 = π/2 and 35π/10 = 7π/2 miles respectively. If x = 10, then t = 4π/50. So the cars would travel 40π/50 = 4π/5 and 160π/50 = 16π/5 miles respectively. As wee see these results define different points along the track. Therefore statement (1) by itself is NOT sufficient. Statement (2) gives us the fact that y = 2x. The relation transforms into xt + 2xt = 4π. So xt = 4π/3. Therefore we know that car A travells 4π/3 miles and car B travels 8π/3 miles. That gives us the definite point along the track, no matter what the values of x and t are. So statement (2) by itself is sufficient. Statement (2) by itself is sufficient to answer the question, while statement (1) by itself is not. The correct answer is B.
_________________
New to the Math Forum? Please read this: Ultimate GMAT Quantitative Megathread  All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
Collection of Questions: PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.
What are GMAT Club Tests? Extrahard Quant Tests with Brilliant Analytics



Math Expert
Joined: 02 Sep 2009
Posts: 51072

Re: In the figure above, car A and car B simultaneously begin travelling..
[#permalink]
Show Tags
19 Jul 2015, 12:34



Intern
Joined: 28 Nov 2012
Posts: 29

Re: In the figure above, car A and car B simultaneously begin travelling..
[#permalink]
Show Tags
15 Oct 2015, 06:25
Hello,
Even with Statement 2 in consideration, the cars will meet at three different points on the circle. Since the question does not ask us about the first meeting point, how can this be answered?
Thanks



Manager
Joined: 10 Apr 2015
Posts: 182
GPA: 3.31

Re: In the figure above, car A and car B simultaneously begin travelling..
[#permalink]
Show Tags
01 Apr 2017, 00:43
In the figure above, car A and car B simultaneously begin travelling around a circular park with area of 4π4π square miles. Both cars start form the same point, the START location shown in the figure, and travel with constant speed rates until they meet. Car A travels counterclockwise and car B travels clockwise. Where along the track will they meet? (Note: figure not drawn to scale). (1) Car B travels 30 mph faster than car A. (2) Car A travels twice as slowly as car B. It is DS ques. (1) says speed of A = x mph B = x + 30 mph x = 5 , x = 50 will yield diff results respectively. NS (2) it gives comparison of speed. we know dis = speed * time we know total dis. ratio of speed, time is same for both. Sufficient.
_________________
In case you find my posts helpful, give me Kudos. Thank you.



NonHuman User
Joined: 09 Sep 2013
Posts: 9097

Re: In the figure above, car A and car B simultaneously begin travelling..
[#permalink]
Show Tags
11 Aug 2018, 16:44
Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up  doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources




Re: In the figure above, car A and car B simultaneously begin travelling.. &nbs
[#permalink]
11 Aug 2018, 16:44






