Question

A parallelogram has an interior angle measuring 81°. Which MUST also be the measure of an interior angle of the parallelogram?

A) 9°
B) 19°
C) 49°
D) 89°
E) 99°

Answer 1

99º, because the sum of all 4 of the interior angles of the parallelogram must be 360º. We know that if one angle measures 81º the other angle on the opposite side must measure 81º.. so 81+81=162
360-162=198
198 - 2(number of remaining angles) = 99º