Question

Three angles of a quadrilateral are ${75}^{\circ },{90}^{\circ }and{75}^{\circ }$. Find the measure of the fourth angle.

Answer 1

Given: Three angles of a quadrilateral are 75°, 90° and 75°.
Let the fourth angle be x.

75° + 90° + 75° + x = 360° ⇒ 240° + x = 360°

⇒ x = 360° - 240° ⇒ x = 120°

So, the measure of the fourth angle is 120°.