Question

Three angles of a quadrilateral are ${60}^{\circ },{120}^{\circ },and{80}^{\circ }.$ Find the fourth angle.

• A. ${60}^{\circ }$
• B. ${80}^{\circ }$
• C. ${120}^{\circ }$
• D. None of the above

Answer 1

The correct option is D None of the above

Let the fourth angle be x.
${60}^{\circ }+{120}^{\circ }+{80}^{\circ }+x={360}^{\circ }$ [sum of all angles of quadrilateral ${360}^{\circ }$]
x = ${100}^{\circ }$.