The sum of angles in a triangle is:

**The reasoning** This is a **fundamental property of Euclidean geometry** — one of the bedrock rules you must memorize. Every triangle, no matter its shape (scalene, isosceles, equilateral, right-angled), has interior angles that add up to exactly **180°**. Think of it practically: If you have a right-angled triangle with one 90° angle and another 60° angle, the third must be 30° because 90° + 60° + 30° = 180°. Or picture an equilateral triangle — three equal angles, so each is 180° ÷ 3 = 60°. **Why the wrong options tempt you** - **90°** — You might confuse this with a *right angle* (one angle in a right triangle), not the sum of all three. - **270°** — Some students mistakenly add an extra angle or think of supplementary relationships. - **360°** — This is the sum of angles in a *quadrilateral* (four-sided shape), not a triangle. Easy mix-up! **Quick takeaway** **Triangle = 180°, Quadrilateral = 360°** — the number of sides increases, so does the angle sum. Lock this in!