Triangles in which all corresponding parts are equal in measure are called

• A. Isosceles triangles
• B. Congruent triangles
• C. Scalene triangles
• D. Similar triangles

Answer: (B)

Equality of all corresponding parts means the two triangles are congruent: they have exactly the same size and shape, so one can be placed on top of the other and they match perfectly. This is what congruent triangles are.

This differs from an isosceles or scalene triangle, which describe properties inside a single triangle (two equal sides or all sides unequal, respectively). Similar triangles have equal corresponding angles and proportional sides, but the side lengths need not be equal—only proportional. Hence, when every corresponding part matches in measure, the triangles are congruent.