The sum of the interior angles, s , in an n minus sided polygon can be determined using the formula s is equal to 180 times open paren n minus 2 close paren , where n is the number of sides. Using this formula, how many sides does a polygon have if the sum of the interior angles is 1,260 degrees ? Round to the nearest whole number.
Substitute 1,260 for s in the formula: 1,260 = 180(n − 2). Divide both sides by 180 to get 7 = n − 2, so n = 9. The polygon has 9 sides, which is choice C.
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