 In the GMAT, circles and its properties is a common question that is asked in the quantitative section. These are just basic Geometry questions that you must have learnt in high-school. Hence, all you need to do is brush up on this topic well, take up some sample questions and practice as much as you can. If you are fresh out of college, revising this topic wouldn’t take you much time but if you are a professional who hasn’t stayed in touch with Geometry for a long time, then you might need to pay extra attention. However, once you learn the concepts and formulas and practice questions well enough, then you can surely solve these problems with ease.  In this article, we will cover some basic concepts of the circle, we will talk about circle properties and also provide some important formulas for you to memorize.   Circle: Basic Concepts  Before we move onto the properties of a circle, let’s understand the basic circle concepts.
1. Radius: The radius refers to a distance between the center and any point on the boundary of the circle. It is identified by the letter “R”.
2. Diameter: The diameter refers to a distance between any two points on the boundary of the circle. It runs across the circle as a line and is identified by the letter “D”. The diameter, when broken down into two parts, becomes two radii. Hence, D= 2R
3. Center: The fixed middle point of the circle is the center.
4. Semi- circle: When the circle is divided into two equal parts, it is referred to as the semi-circle.
5. Circumference: The circumference refers to the area that boundaries the circle.
6. Arc: The arc of the circle refers to any two pints on the circumference. There are two kinds of arcs— minor and major arcs. If the distance between two points is shorter, then it becomes a minor arc and the remaining arc of the circle is the major arc.
7. Sector: When the two ends of arc meet at the center of the circle, the area within is known as a sector. Yet again, there are two kinds of sectors— major and minor sectors.