Last visit was: 02 Jun 2026, 02:07 It is currently 02 Jun 2026, 02:07
Home
Messages
MBA Fair
Tests
Schools
Events
Close
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel
User avatar
enfinity
User avatar
Joined: 12 May 2009
Last visit: 12 Oct 2014
Posts: 41
Own Kudos:
241
Given Kudos: 18
Posts: 41
Kudos: 241
Circle: Area triples, what happends to the radius (MGMAT) 20 Sep 2009, 07:03
Kudos
Add Kudos
Bookmarks
Bookmark this Post
00:00
Start Timer
Pause Timer
Resume Timer
Show Answer
Hide
Show
History
N
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

Difficulty:

(N/A)

Question Stats:

67% (00:51) correct 33% (01:37) wrong based on 4 sessions

History

Date
Time
Result
Not Attempted Yet
Hi there,

I found a very useful document on the MGMAT website. However, I think they made a mistake in one of their sample problem so I just want some confirmation that this is indeed a mistake...

Here the link: https://www.manhattangmat.com/strategy- ... oncept.cfm

Here the problem:
Quote:
At a certain barn, the horses exercise in one of two circular arenas using what is called a lunge rope. A trainer stands in the center of the circular arena holding a rope attached to the horse, and the horse runs in a circular path along the perimeter of the arena. Assuming negligible distance between the horse's path of motion and the edge of the arena, approximately how many times as much rope is needed to lunge a horse in the larger arena if the larger arena has an area three times that of the smaller one?

(A) 1.5
(B) 1.7
(C) 2
(D) 3
(E) 6


MGMAT SOLUTION:
The formula for the area of a circle is A=pi*r^2. Mathematically, this means that the area of a circle is proportionate to the square of the radius. If the radius of a circle is doubled, the area of the circle will be quadrupled. If the radius of a circle is tripled, the area of the circle will multiply by a factor of 9. We can represent this relationship in a proportion:

A1/A2=r1^2/r2^2

Let's call circle 1 the smaller circle. We know that the ratio of the areas in this question is 1:3. Since it is simply the ratio of the radii that we are concerned with in this question, we can assign a random value of 1 as the radius of the smaller circle and solve for x, the radius of the larger circle.
Show more

I marked the part that I do not agree with. They simply say that 1=pi*1^2 (this equation is never true). Did I miss something or is this indeed a mistake.



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Problem Solving (PS) Forum
Still interested in this question? Check out the "Best Topics" block below for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
User avatar
enfinity
User avatar
Joined: 12 May 2009
Last visit: 12 Oct 2014
Posts: 41
Own Kudos:
241
Given Kudos: 18
Posts: 41
Kudos: 241
Circle: Area triples, what happends to the radius (MGMAT) 20 Sep 2009, 07:04
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Ok, I think I got it (they're just comparing the ratios on the right side). So it should be correct.



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Problem Solving (PS) Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
Moderator:
Bunuel
Math Expert
111020 posts