FTCE General Knowledge Math Practice Test

Which type of triangle has one angle measuring between 90° and 180°?

1. Acute triangle

2. Obtuse triangle

3. Scalene triangle

4. Right triangle

The correct answer is: Obtuse triangle

A triangle that has one angle measuring between 90° and 180° is classified as an obtuse triangle. This type of triangle is characterized by having one angle that exceeds 90°, making it "obtuse," while the other two angles are acute (less than 90°) to satisfy the triangle inequality theorem, which states that the sum of the interior angles of a triangle must equal 180°. In contrast, an acute triangle has all angles measuring less than 90°, a scalene triangle has all sides and angles of different lengths and measures, and a right triangle contains exactly one angle that measures exactly 90°. These definitions help differentiate the obtuse triangle from the other types based on their angle measurements.