This Instructional Activity is a part of the Lesson 12, Unit 3, Grade 8. Students work in small groups to model the use of similar triangles in real-world problems. Exercise 1 is classified as an ill-defined modeling task because some of the information in the problem is not absolutely clear. The purpose of this is to motivate students to discuss in their groups what is meant by "straight down," whether or not it is safe to assume that the building is perpendicular to the ground, and whether or not it is safe to assume that the person is standing perpendicular to the ground. These kinds of mathematical discussions should be encouraged as they demonstrate students' learning of a topic. Mathematical Modeling Exercises 1-3 1.