# Finding the Missing Angles in a Quadrilateral.

The sum of angles in a quadrilateral is 360°. Using the same concept for determining angels that we used to determine the missing angle of a triangle, we can find the missing angle in a quadrilateral.

There are four angles in a rectangle. We know three of them: 70°, 55°, 110°.

What is the missing angle? Using the known information, we can determine the missing angle.

Attempt #1

70 + 55 + 110 = 235

235+ ? = 360

235 + 125 = 360

The missing angle is 125°.

Attempt #2

360- 70-110-55 = ?

360- 70 = 290

290 – 110 = 180

180 – 55 = 125°

The missing angle is 125°