Which triangle has all sides of equal length?

• A. Isosceles
• B. Right
• C. Equilateral
• D. Scalene

Answer: (C)

A triangle with all sides of equal length is classified as an equilateral triangle. In this type of triangle, not only are the sides equal, but the angles are also all equal, each measuring 60 degrees. This symmetry gives the equilateral triangle its unique properties, which include the fact that it has a specific relationship between the sides and the angles.

Understanding the characteristics of other triangle types helps clarify why equilateral is the correct option. An isosceles triangle has two sides of equal length and one side that is different, thus it cannot have all sides equal. A right triangle specifically has one angle measuring 90 degrees and does not necessarily require all sides to be equal. A scalene triangle, on the other hand, features all sides of different lengths. Therefore, the defining criterion of the equilateral triangle is that it maintains equality in both sides and angles, which is why this is the correct classification.