Question

(iv)
In a parallelogram ABCD, the measure of A is 20°
more than thrice the measure of B. Find the
measure of C and D.​

Answer 1

let the measure of angle B be x.

therefore, the measure of angle A = 3x+20°

angle A + angle B = 180°(sum of Co interior angles)

(3x+20)°+x = 180°

3x +x = 180°-20°

4x = 160°

x = 160°/4

x = 40 °

thus, angle B = 40°

angle A = 3x +20° = 3×40°+20° =120°+20° = 140°

angle C = angle A = 140°(opposite angles of parallelogram)

angle D = angle B = 40°(opposite angle of parallelogram are equal)