Question 153393
The measure of an interior angle of a regular polygon of n sides is given by:
{{{A[i] = (n-2)180/n}}} In this problem, the interior angle is 120 degrees, so...
{{{(n-2)180/n = 120}}} Simplify and solve for n. Multiply both sides by n.
{{{(n-2)180 = 120n}}} Expand the left side.
{{{180n-360 = 120n}}} Subtract 120n from both sides.
{{{60n - 360 = 0}}}  Now add 360 to both sides.
{{{60n = 360}}} Finally, divide both sides by 60.
{{{n = 6}}}
The regular polygon has 6 sides, and this is called a hexagon.