Which statement is true about an equilateral triangle?

Which statement is true about an equilateral triangle?

• A. All three sides are equal.
• B. All three angles are 120 degrees.
• C. It has a right angle.
• D. Two sides are congruent.

Answer: (A)

Equilateral triangles are defined by having all sides the same length. That equal-length property directly implies all three interior angles are equal, and since the angle sum is 180 degrees, each angle measures 60 degrees. So the angles are not 120 degrees, and there isn’t a right angle. Saying two sides are congruent is true for many triangles as well (isosceles), but it doesn’t uniquely identify an equilateral triangle. The statement that all three sides are equal captures the defining feature of an equilateral triangle, making it the best choice.

Equilateral triangles are defined by having all sides the same length. That equal-length property directly implies all three interior angles are equal, and since the angle sum is 180 degrees, each angle measures 60 degrees. So the angles are not 120 degrees, and there isn’t a right angle. Saying two sides are congruent is true for many triangles as well (isosceles), but it doesn’t uniquely identify an equilateral triangle. The statement that all three sides are equal captures the defining feature of an equilateral triangle, making it the best choice.