Question

In a quadrilateral, three of the angles are obtuse. Which of the following could not be the angle measure of the fourth angle?

20°
40°
60°
90°

Answer 1

If an angle it is obtuse it is between 90 and 180.

Angles in a quadrilateral add up to 360.

Therefore 3 obtuse angles must add up to AT LEAST 273 and if you then added the 90 it would get you to 363 which is too large so it cant be 90 :)