Question

For the given equilateral triangle, calculate the sum of the exterior angles $\angle B$ and $\angle C$.

• A. ${120}^{\circ }$
• B. ${180}^{\circ }$
• C. ${240}^{\circ }$
• D. ${210}^{\circ }$

Answer 1

The correct option is C ${240}^{\circ }$

The given equilateral triangle is

All the angles of an equilateral triangle are equal and their value is ${60}^{\circ }$.

Therefore, all the exterior angles will be equal too.

Sum of all the exterior angles of a triangle is equal to ${360}^{\circ }$.

$\angle A+\angle B+\angle C={360}^{\circ }$

$3\times \angle A={360}^{\circ }$ (All angles are equal)

$\angle A=\frac{{360}^{\circ }}{3}={120}^{\circ }$

$\angle A=\angle B=\angle C={120}^{\circ }$

Therefore, $\angle B+\angle C={120}^{\circ }+{120}^{\circ }={240}^{\circ }$