An exterior angle of a triangle is 140 degrees. If the non-adjacent angles are congruent, then what are the measures of all of the interior angles of the triangle?

The measures of all of the interior angles of the triangle are 70 degrees, 70 degrees and 40 degrees

Solution:

Given that exterior angle of triangle is 140 degrees

The exterior angle of a triangle is equal to the sum of the measures of the two non-adjacent interior angles

Given that adjacent angles are congruent

Let one of the non adjacent interior angles be "x"

x + x = 140

2x = 140

x = 70

So the two interior angles are 70 degrees and 70 degrees

Let us find the third interior angle

The angle sum property of a triangle states that the interior angles of a triangle always add up to 180 degrees

70 + 70 + third angle = 180

third angle = 180 - 70 - 70

third angle = 180 - 140

third angle = 40 degrees

Thus the measures of all of the interior angles of the triangle are 70 degrees, 70 degrees and 40 degrees