Question

Find the unknown marked angles in the given figure:

Answer 1

∠B + ∠ABC = 180°    ...(Linear pair)

∠B + 140° = 180°

∠B = 180° − 140°

∠B = 40°

Exterior angle = sum of its interior opposite angles.

2m + 40° = 4m

2m − 4m = −40°

−2m = −40°

2m = 40°

m = `40/2`

m = 20°

∠A = 2m = 2 × 20° = 40°

∠B = 40°

∠D = 4m = 4 × 20° = 80°