# Activities

• • • ##### Subject Area

• Math: Geometry: Points, Lines and Angles

• ##### Author 6-8

60 Minutes

• ##### Device
• TI-73 Explorer™
• ##### Other Materials
This is Activity 10 from the EXPLORATIONS Book:
Discovering Mathematics with the TI-73: Activities for Grades 7 And 8

The following materials are required for this activity:
• A set of stairs with at least 3 stairs, or 6 congruent shoe boxes
• Ruler with centimeters and inches
• String and tape

## Step Up

#### Activity Overview

Students learn to use measurements on a real model to develop the concept of slope and linear functions. They use a calculator to explore changing the slopes and Y- intercepts in the slope intercept form Y = MX + B.

#### Before the Activity

• See the attached PDF file for detailed instructions for this activity
• Print pages 89 - 94 from the attached PDF file for your class
• #### During the Activity

Distribute the pages to the class.

• Measure the vertical height (rise) and the horizontal height (run) of stairs in centimeters and inches
• Use centimeters and inches conversion to verify accuracy of the measurements
• Enter the values on the calculator and draw a model of the staircase
• Use the Manual-Fit function to draw a line from the tip of the first step to the tip of the third step
• Find the equation of the line drawn in the form of Y = MX + B
• From the equation of the line, find the value of M, the coefficient of X, which is the slope, and the value of B, the y-intercept
• Change the values of B and M and note the change in the lines
• #### After the Activity

Students will complete the Worksheet and analyze the results.

Review student results:

• As a class, discuss questions that appeared to be more challenging
• Re-teach concepts as necessary