Question

If ABCD is a parallelogram and angle B=100 degree, then find the value of angle A angle C

Answer 1

If ABCD is IIgm having angle b as 100 degree then angle A will be 80 degree as in a IIgm adjacent angles are supplementry.Angle C will be 80 degree too as angle A and Angle C are opposite angles which are equal in a IIgm. Hope it helps and pls mark as the best answer. :)

Answer 2

if ABCD is a parallelogram the,
∠B = 100°
∴ ∠D = 100° 
and,
∠A = ∠C = ∠x ( we have let ∠A and ∠C as ∠x )
since opposite angles of a parallelogram is equal. 
and,
∠A +∠B + ∠C +∠D = 360°
since angle sum property of a parallelogram is 360°
∠x + ∠x + 100° + 100° = 360°
⇒2∠x + 200° = 360°
⇒2∠x = 360° - 200°
⇒2∠x = 160°
⇒∠x = 160/2
⇒∠x = 80°
therefore ∠A = 80° and ∠C = 80°
   i hope that this will help u.............................^_^