Question

If ${56}^{\circ }$ and ${85}^{\circ }$ are the two interior angles of a triangle, then the third angle is ______.

• A. ${79}^{\circ }$
  
• B. ${29}^{\circ }$
  
• C. ${39}^{\circ }$
  
• D. ${49}^{\circ }$
  

Answer 1

The correct option is C ${39}^{\circ }$


The sum of the interior angles of a triangle = ${180}^{\circ }$

$\Rightarrow$ ${56}^{\circ }+{85}^{\circ }+thirdangle={180}^{\circ }$


$\Rightarrow$ $thirdangle={180}^{\circ }-{56}^{\circ }-{85}^{\circ }$

$\Rightarrow$ $thirdangle={39}^{\circ }$