Question

In the given figure, $\angle ABD={70}^o,\angle ADB={30}^o$. Then $\angle BCD$ is __________.

• A. ${90}^o$
• B. ${80}^o$
• C. ${100}^o$
• D. ${120}^o$

Answer 1

Answer: (C)

${100}^o$

$\angle BAD=180-(\angle ADB+\angle ABD)=180-30-70={80}^o$

$\angle BAD$ and $\angle BCD$ are supplementary angles.

$\therefore \angle BCD={180}^o-\angle BAD=180-80={100}^o$