California Assessment of Student Performance and Progress (CAASPP) Math Practice Exam

What type of triangle has one angle that measures exactly 90 degrees?

1. Scalene triangle

2. Obtuse triangle

3. Equilateral triangle

4. Right triangle

The correct answer is: Right triangle

A triangle with exactly one angle measuring 90 degrees is classified as a right triangle. This specific type of triangle adheres to the Pythagorean theorem, where the square of the length of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the other two sides. This unique characteristic differentiates it from other types of triangles, as a right triangle is defined specifically by the presence of that one right angle. In contrast, a scalene triangle has all sides of different lengths and does not necessarily have any angles measuring exactly 90 degrees. An obtuse triangle features one angle that measures more than 90 degrees, which again rules out the possibility of it being a right triangle. An equilateral triangle, on the other hand, has all three angles measuring exactly 60 degrees, which does not allow for any angles to reach the 90-degree mark. Thus, the defining feature of having one angle that is exactly 90 degrees directly points to the right triangle as the correct answer.