Question

Two angles of a triangle have measures of 55° and 65°.

Which could not be a measure of an exterior angle of the
triangle?

A. 120
B.125
C.130
D.115

Answer 1

C

Explanation:

an exterior angle is supplementary to the adjacent interior angle.

So 180 - 55 = 125

180 - 65 = 115

The third angle of your triangle is 180 - 55 - 65 = 60

180 - 60 = 120

C is the only value that cannot be the measure of an exterior angle.