equilateral triangel

Expert replies

vivek.kapoor83: Legendary Member; Posts: 833; Joined: Mon Aug 04, 2008 1:56 am; Thanked: 13 times

by vivek.kapoor83 » Wed Jan 07, 2009 7:20 am

If an equilateral triangle ABC is inscribed in a circle .Length of Arc ABC =24
Wht is the diameter of circle.

Im getting ans 24
OA is 11

Like this post

Source: Beat The GMAT — Problem Solving | Wed Jan 07, 2009 7:20 am

sonu_thekool: Senior | Next Rank: 100 Posts; Posts: 60; Joined: Mon Jun 04, 2007 7:37 am; Thanked: 6 times

by sonu_thekool » Wed Jan 07, 2009 9:06 am

I got 11.464 approx equal to 11 but I am not sure if what I did is the right approach....

I have attached a diagram and steps...I am sure there is a better approach...

Attachments

CircleArc.pdf: CircleArc; (16.38 KiB) Downloaded 99 times

Like this post

vivek.kapoor83: Legendary Member; Posts: 833; Joined: Mon Aug 04, 2008 1:56 am; Thanked: 13 times

by vivek.kapoor83 » Wed Jan 07, 2009 9:24 am

pls reply

Attachments

Like this post

vivek.kapoor83: Legendary Member; Posts: 833; Joined: Mon Aug 04, 2008 1:56 am; Thanked: 13 times

by vivek.kapoor83 » Wed Jan 07, 2009 9:35 am

why u have taken other angle 240 what is wrong with my sol

Like this post

sonu_thekool: Senior | Next Rank: 100 Posts; Posts: 60; Joined: Mon Jun 04, 2007 7:37 am; Thanked: 6 times

by sonu_thekool » Wed Jan 07, 2009 10:40 am

Vivek,

By taking 120 degrees, you are measuring the arc length of AC (in my diagram attached, that is the dotted line) while you dont know what that value is. The only info you know is about arc ABC (the dark solid line).

Since 120 + x = 360 at the center, x = 240.

As you already know the length of an arc = angle at the center formed by the two radii intersecting (OA and OB).

240 is the angle that complements the 120 in the center.

So, 240/360 * 2 pi r = 24

2 pi r or pi * d = 36

d = 36/pi = 11.46

Hope this helps.

Like this post

iamcste: Legendary Member; Posts: 940; Joined: Tue Aug 26, 2008 3:22 amFollowed by: 1 member; Thanked: 55 times

by iamcste » Wed Jan 07, 2009 10:45 am

Refer

https://www.beatthegmat.com/equilateral- ... tml#112083

Like this post

vivek.kapoor83: Legendary Member; Posts: 833; Joined: Mon Aug 04, 2008 1:56 am; Thanked: 13 times

by vivek.kapoor83 » Wed Jan 07, 2009 11:14 am

Sonu,
cn u explain this in my diagram,coz in my diagram 120 degree include whole ABC arc...

Like this post

sonu_thekool: Senior | Next Rank: 100 Posts; Posts: 60; Joined: Mon Jun 04, 2007 7:37 am; Thanked: 6 times

by sonu_thekool » Wed Jan 07, 2009 11:40 am

In your diagram, your 120 is the angle referring to bottom portion of the circle (the portion below the base of your triangle) - arc AC, no info is given about that.

All we know if about length of arc ABC (24) - the top portion - the portion from the base of your triangle all the way around the circle, whose angle at the center is 240.

So, 240/260 * 2 pi r = 24

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review