Question

If two angles of a triangle are 105° and 15°,then the third angle is ____.

• A. 75
• B. 25°
• C. 60
• D. None of the above

Answer 1

The correct option is C 60

In the $△ABC,$ using angle sum property:

$\angle A+\angle B+\angle C={180}^{\circ }$

$\Rightarrow \angle C={180}^{\circ }-\angle A-\angle B$

$=180-105-15={60}^{\circ }$

$\Rightarrow \angle C={60}^{\circ }$

Hence the third angle is ${60}^{\circ }$