Strategies, Sample Questions, and Random Ramblings.
July 19, 2015
Circles are another favorite of the GMAT test writers. You might think that this should be a no brainer topic as there are only two formulas and a couple of terms that most of us learned about circles, but the integration of other geometry concepts is what makes gmat circle problems tough - and the few things you might not remember from high school.
A term that you absolutely must know is π . The approximate value of π is 3.14. This may come into play in some calculations in DS problems, but realistically all you need to remember is that π is just a bit bigger than 3. Also, know that there are 360° in angle measurements around the center of the circle. The following definitions will be paramount to your success with circle questions. The first four are the most common, but the remaining will be key to understand as you reach more difficult problems.
Radius or r : The distance from the center of the circle to the edge
Diameter or d : twice the length of the radius and splits the circle in two
Area of a Circle = πr^2
Circumference of a Circle: 2πr or πd , length of the line going around the circle
Central Angle: An angle created by two radii of a circle
Arc: A curved line that is part of the circumference of a circle
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