Canadian Forces Aptitude Test (CFAT) Practice 2025 - Free CFAT Practice Questions and Study Guide

The sum of the internal angles of a triangle is universally established as 180 degrees. This rule is derived from the properties of Euclidean geometry, which states that any triangle—regardless of its type (scalene, isosceles, or equilateral)—will always have internal angles that add up to this specific measurement.

To understand why the sum is 180 degrees, consider that if you take a triangle and extend one of its sides, you can create a straight line. A straight line measures 180 degrees, and the angles adjacent to the extended angle of the triangle account for the total, confirming the total internal angle measurement of the triangle itself.

The other options are incorrect because they do not reflect the fundamental properties of triangles in Euclidean space: 90 degrees would suggest a right angle configuration only; 360 degrees pertains to a full circle rather than the confines of a triangle; and 270 degrees also surpasses the total possible for any triangle's internal angles. This consistent 180-degree rule is a foundational concept in geometry applicable in various contexts.