Question

Find the missing angle of the triangle:
${110}^{\circ },{55}^{\circ }$,

• A. ${15}^{\circ }$
• B. ${25}^{\circ }$
• C. ${20}^{\circ }$

Answer 1

The correct option is A ${15}^{\circ }$

We know: Sum of angles of a triangle is equal to ${180}^{\circ }$.
$\because m\angle A+m\angle B+m\angle C={180}^{\circ }$
$\Rightarrow m\angle C={180}^{\circ }-(m\angle B+m\angle C)$
First we will add up the two angles of the triangle:



Then we subtract the sum from $180$:


So, the value of the missing angle is $15$ degree.