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GMAT Geometry: Central Angles

June 28, 2012 by

In poetry, a rose is a rose is a rose. On GMAT problems with central angle “slices” in circles, a fraction is a fraction is a fraction.

This may seem like common sense. Cut a pizza into six slices. If you cut it evenly, each slice now has one-sixth the cheese, one sixth the crust, and an angle of one sixth the way around a circle—that is, 60 degrees.  However, though this may seem obvious, it’s actually a very useful technique for resolving certain geometry problems.

Consider the following Data Sufficiency question:

In a radius 6 circle, two points A and B are connected to the center, point O. What is angle AOB?

1)    The length of the minor arc defined by sector O is 1.5π

2)    The area of the sector defined by angle AOB is 4.5π

It looks all GMAT-like and formal, but if you actually … Read full post

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