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## ds test5 #21

This topic has 4 member replies
dunkin77 Master | Next Rank: 500 Posts
Joined
01 Apr 2007
Posted:
269 messages

#### ds test5 #21

Fri Apr 06, 2007 5:04 pm
Hi,

the answer to the attached question is C). Although we don't need to get exact number, I am curious how to get circumference of the circle??

Thank you!
Attachments

dunkin77 Master | Next Rank: 500 Posts
Joined
01 Apr 2007
Posted:
269 messages
Sun Apr 08, 2007 7:38 pm
Thank you for patiently explaining all this. I understnd finally

Princeton Review GMAT Instructor
Joined
16 Mar 2007
Posted:
22 messages
Sun Apr 08, 2007 5:01 pm
Well, the arc length that they give us is for major arc XYZ, if I'm reading the problem correctly. Since the angle for minor arc XZ would be 120, then the remaining angle for major arc XYZ would be 240. So 240/360 = 18/Circumference, so the circumference would be 27.

_________________
Matt McIver

Princeton Review Instructor

Princeton Review GMAT Instructor
Joined
16 Mar 2007
Posted:
22 messages
Sat Apr 07, 2007 5:54 am
The central angle of the arc would be formed by drawing radii from the endpoints of the arc (X and Z) to the center of the circle (let's call it O). The arc will be proportional to the circumference of the circle as the central angle is proportional to 360. To put that another way:

(arc/circumference) = (central angle/360)

So if we have the measure of the central angle and the length of the arc, we know the circumference.

Well Statement 1 gives us the arc. Great.

Statement 2 tells us that inscribed angle r = 60, since it is equal to the other two angles in the triangle shown.

The inscribed angle r will be half of the measure of the central angle of the arc. That means that the central angle of the arc = 120, and that's what we need to know.

_________________
Matt McIver

Princeton Review Instructor

dunkin77 Master | Next Rank: 500 Posts
Joined
01 Apr 2007
Posted:
269 messages
Sat Apr 07, 2007 4:57 pm

so, circumference would be..

6/x=120/360
x=18 ...?

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