Question

The measures of three angles of a quadrilateral are 80, 90, and 103 degrees. Find the measure of the fourth angle.

A) 67
B) 77
C) 87
D) 97

Answer 1

C) 87

Step-by-step explanation:

the total sum of the internal angles of a quadrilateral is 360 degrees. Therefore, we must have:

`a+b+c+d+=360` (1)

In this problem, we know three of the angles:

`a=90\\b=90\\c=103`

so, we can re-arrange eq.(1) to solve for d, the missing angle:

`d=360-a-b-c-=360-80-90-103=87`