# Activities

• • • ##### Subject Area

• Math: Elementary Math: Geometry

• ##### Author K-5

60 Minutes

• ##### Device
• TI-10
• TI-15 Explorer™
• ##### Other Materials
This is Activity 21 from the EXPLORATIONS Book:
Uncovering Math with Manipulatives, the TI-10, and the TI-15 Explorer

The following materials are required for this activity:
• Ruler, string or measuring tape, and meter stick
• Pencils
• String and caliper

Predicting π

#### Activity Overview

Students explore the use of linear measurement and calculators to discover the existence of π, the constant ratio between the circumference and the diameter of a circle.

#### Before the Activity

• See the attached PDF file for detailed instructions for this activity
• Print student activity sheet page 102 from the attached PDF file for your class
• #### During the Activity

Distribute the page to the class.

Follow the activity procedures:

• Identify several circular objects in the classroom, on the school grounds, or at home
• Select a tool to measure the circumference and diameter of each circle, and record these measurements on the recording sheet
• Use a compass to draw several different circles and record their circumferences and diameters on the recording sheet
• Calculate the ratio between the circumference and diameter of each circle
• Look for patterns in the data and make conjectures about why the patterns might exist
• Discover the existence of π, the constant ratio between the circumference and the diameter of a circle
• #### After the Activity

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