A triangle which has all the sides unequal is called scalene triangle. In other words, a scalene triangle has no congruent sides. If the sides of a triangle are equal, then the angles formed by the sides are also equal in measurement. So, a scalene triangle has three unequal angles. The sum of three unequal angles is 180 degrees. The perimeter of a scalene triangle is calculated by adding the measurements of all three sides.