Question

Find $\angle A$ in the figure given below.

• A. 80°
• B. 60°
• C. 50°
• D. 70°

Answer 1

The correct option is B 60°

Given,
In $△DEF,$
$\angle D=60°$
$\angle F=70°$

We know that, sum of all the interior angles of a triangle is 180°.

Therefore,
$\angle E=180°-(60°+70°)$
$\angle E=50°$


In $△ACB\text{and}△DEF$,

• CB = EF .... (Given)
• $\angle C=\angle E=50°$ .... (Given)
• AC = DE .... (Given)

So, by SAS criteria for congruency of triangles,
$△ACB\cong △DEF$

Thus,
$\angle A=\angle D=60°$ ... (Corresponding parts of congruent triangles)