# SAT Math: Geometry

## Polygons

If the sum of the interior angle of a regular polygon is 1,260 degrees, how many sides does the polygon have?

A.  6

B.   8

C.   9

D.   12

E.   14

## Knowsys Method

Read the question carefully.  You know that in a regular polygon, all the sides have the same length and all of the angles have the same measure.

Identify the bottom line. # of sides = ?

Assess your options. You should use the polygon rule to find the answer.  The polygon rule is:

total degrees = 180(n - 2)

The variable "n" represents the number of vertices, which is equal to the number of sides for a regular polygon.

Attack the problem.

total degrees = 180(n - 2)

1,260 = 180(n - 2)

7 = n - 2

9 = n

Loop back.  The number that you found represents both the number of angles and the number of sides, so you are done!

The correct answer is (C).

This is a medium level question.

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