Question

Q.9. A quadrilateral has three acute angles, each measure 80o . What is the measure of the fourth angle?

Answer 1

Let ABCD be the quadrilateral
    angle A = angle B = angle C = 80o
    angle D = ?
 
     angle A + angle B + angle C + angle D = 360o
       80o + 80o + 80o + angle D = 360o
        240o + angle D = 360o
          angle D = 120o