Question

In the figure, AOB is a straight line. The measure of $\angle COD$ is equal to :

• A. ${60}^{\circ }$
• B. ${80}^{\circ }$
• C. ${120}^{\circ }$
• D. ${160}^{\circ }$

Answer 1

Answer: (A)

${60}^{\circ }$

$AOB$ is a straight line

$\therefore \angle AOC+\angle COD+\angle DOB={180}^{\circ }$

$\Rightarrow x+{20}^{\circ }+2x-{20}^{\circ }+{60}^{\circ }={180}^{\circ }\Rightarrow 3x={120}^{\circ }\Rightarrow x={40}^{\circ }\angle COD=2x-{20}^{\circ }=(2\times {40}^{\circ })-{20}^{\circ }={60}^{\circ }$