In this third of four lessons related to triangles, students use strips of paper divided into three segments of various lengths to see which strips can form triangles. The goal is for students to discover the triangle inequality, namely, that the sum of the lengths of any two sides must exceed the length of the other side.

In this third of four lessons related to triangles, students use strips of paper divided into three segments of various lengths to see which strips can form triangles. The goal is for students to discover the triangle inequality, namely, that the sum of the lengths of any two sides must exceed the length of the other side. An activity sheet and problem extensions are included. This lesson is adapted from an article that appeared in the November 1993 issue of Arithmetic Teacher. (sw)