Question

If two angles of triangle measure ${100}^0$ and ${40}^0$, then the third angle is ______.

• A. ${20}^{\circ }$
• B. ${30}^{\circ }$
• C. ${40}^{\circ }$
• D. ${50}^{\circ }$

Answer 1

The correct option is C ${40}^{\circ }$

Sum of interior angles of any triangle is always ${180}^{\circ }$.
Given the angles are ${100}^{\circ }$ and ${40}^{\circ }$.
${100}^{\circ }$ + ${40}^{\circ }$ + x = ${180}^{\circ }$
${140}^0$ + x = ${180}^0$
$x={180}^{\circ }-{140}^{\circ }x={40}^{\circ }$

Hence, the third angle of the triangle is ${40}^{\circ }.$