Question:
Three angles of a quadrilateral are 80°, 95° and 112°. Its fourth angle is
(a) 78°
(b) 73°
(c) 85°
(d) 100°
Solution:
(b) 73°
Explanation:
Let the measure of the fourth angle be xo.
Since the sum of the angles of a quadrilateral is 360o, we have:
80o + 95o + 112o + x = 360o
⇒ 287o + x = 360o
⇒ x = 73o
Hence, the measure of the fourth angle is 73o.