Question

In a right-angled triangle, if an angle measures ${30}^{\circ }$, then the measure of the third angle is:

• A. ${120}^{\circ }$
• B. ${40}^{\circ }$
• C. ${60}^{\circ }$
• D. ${45}^{\circ }$

Answer 1

The correct option is C

${60}^{\circ }$

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

Given: One angle is 90${}^{\circ }$(since it is a right angled triangle ) and another angle is 30${}^{\circ }$

Hence, ${90}^{\circ }+{30}^{\circ }+\text{Third angle}={180}^{\circ }$

$\Rightarrow {120}^{\circ }+\text{Third angle}={180}^{\circ }$

$\therefore \text{Third angle}={180}^{\circ }-{120}^{\circ }={60}^{\circ }$