This Instructional Activity is a part of the Lesson 8, Unit 4, Grade 7. The class discusses the dimensions of a computer monitor's size. The length of the diagonal of the screen tells the screen's size. Before discussion, select three students to measure the diagonal of a 15-inch screen (in inches) using a ruler. A sample list of each student's measurement is recorded in a list below. If a 15-inch monitor is not available, use another size.