Question:
In ∆ABC, side BC is produced to D. If ∠ABC = 50° and ∠ACD = 110° then ∠A = ?
(a) 160°
(b) 60°
(c) 80°
(d) 30°
Solution:
$\therefore \angle A+\angle B=\angle A C D$
$\Rightarrow \angle A+50^{\circ}=110^{\circ}$
$\Rightarrow \angle A=60^{\circ}$
Hence, the correct answer is option (b).