BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Circle

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 30
Joined: Wed May 07, 2008 6:16 am

Circle

by bia » Sun May 18, 2008 5:18 am
My answer is : 4sqrt(3). Anyone has the same answer as I ?

The points R,T and U lie on a circle that has radius 4. If the length of arc RTU is 4pi/3, what is the length of line segment RU?
A. 4/3
B. 8/3
C. 3
D. 4
E. 6
Bia
Top
Source: — Problem Solving |
Senior | Next Rank: 100 Posts
Posts: 84
Joined: Tue Feb 05, 2008 8:52 pm
Thanked: 8 times

by luvaduva » Sun May 18, 2008 4:32 pm
I get B) 4.

Basically, you use the fact that the arc length is 1/6 the circumference to determine that the angle of the arc is 60 and use 30-60-90 triangle properties.

A picture is worth a thousand words so...


Image
Top
Senior | Next Rank: 100 Posts
Posts: 30
Joined: Wed May 07, 2008 6:16 am

by bia » Sun May 18, 2008 9:20 pm
Ok, I'm wrong in calculating arc RTU. Thanks
Bia
Top
Legendary Member
Posts: 631
Joined: Mon Feb 18, 2008 11:57 pm
Thanked: 29 times
Followed by:3 members

by netigen » Mon May 19, 2008 12:40 am
no need to complicate such a simple problem.

when we find out that the arc angle is 60 we know that the triangle is an equilateral triangle. This means all sides should be equal hence RU=4
Top
Master | Next Rank: 500 Posts
Posts: 468
Joined: Sat Mar 03, 2007 10:17 pm
Thanked: 5 times

by moneyman » Mon May 19, 2008 5:58 am
Hi Netigen..how did u conclude that if the triangle is an equilateral triangle ? It can be a 30-60-90 as well right ? Or am I missing something ?
Maxx
Top
User avatar
GMAT Instructor
Posts: 3225
Joined: Tue Jan 08, 2008 2:40 pm
Location: Toronto
Thanked: 1710 times
Followed by:614 members
GMAT Score:800

by Stuart@KaplanGMAT » Mon May 19, 2008 9:26 am
moneyman wrote:Hi Netigen..how did u conclude that if the triangle is an equilateral triangle ? It can be a 30-60-90 as well right ? Or am I missing something ?
Every triangle formed with 2 radii is going to be isosceles, since radius = radius. The two angles NOT at the centre of the circle will always be equal. If we let "c" be the angle at the centre and x be the two angles on the circumference, we know that:

180 = c + 2x

In this question, c = 60, so

180 = 60 + 2x
120 = 2x
60 = x

So, our triangle must be 60/60/60, i.e. equliateral.
Image

Stuart Kovinsky | Kaplan GMAT Faculty | Toronto

Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course
Top
Post new topic Post Reply
• Page 1 of 1