Question

Three interior angles of a quadrilateral measure 55°, 117°, and 120°. What is the measure of the fourth interior angle?

68°
78°
88°
98°

Answer 1

68

Explanation:

The sum of the interior angles of a quadrilateral is 360. The sum of the interior angles or a triangle is 180. If you think about a rectangle, you can cut that up into two triangles, so 180 + 180 = 360.

Now subtract out the 3 angles that you know

360-55-117-120 = 68

Answer 2

68

Explanation:

We know the sum of interior angles for a quadrilateral must equal 360, so we can create the following equation

`55+117+120+x=360`

Simplify

`292+x=360`

Subtract 292 from both sides

`x=68`