Question

If two angles in a triangle are ${40}^o$ and ${60}^o$, then the third angle is:

• A. ${90}^o$
• B. ${80}^o$
• C. ${70}^o$
• D. ${60}^o$

Answer 1

Answer: (B)

${80}^o$

Let the third angle be $x$

We know, by angle sum property, the sum of all angles of a triangles is ${180}^0$.

${40}^{\circ }+{60}^{\circ }+x={180}^{\circ }{100}^{\circ }+x={180}^{\circ }\Rightarrow x={80}^{\circ }$