Question

In a triangle, if the sum of two angles is ${150}^{\circ }$, what is the third angle equal to?

• A. ${120}^{\circ }$
• B. ${150}^{\circ }$
• C. ${90}^{\circ }$
• D. ${30}^{\circ }$

Answer 1

The correct option is D ${30}^{\circ }$

From Legendre's theorem:
The sum of all the three angles of a triangle is equal to ${180}^{\circ }$.
$\Rightarrow$ The third angle = ${180}^{\circ }$ - ${150}^{\circ }$
= ${30}^{\circ }$.