# Activities

• • • ##### Subject Area

• Math: PreAlgebra: Number Sense and Operations

• ##### Author 6-8

60 Minutes

• ##### Device
• TI-73 Explorer™
• ##### Other Materials
This is Activity 8 from the EXPLORATIONS Book:
Walking the Line: Activities for the TI-73 Number Line.

## Somewhere In Between

#### Activity Overview

In this activity, students develop estimation and mental arithmetic skills for integer addition and subtraction. In this activity, the Number Line application will be used for targeting estimations.

#### Before the Activity

• Access the NUMLINE application and select the Number Line option
• See the attached PDF file for detailed instructions for this activity
• Print pages 59 - 62 from the attached PDF file for your class

#### During the Activity

Distribute the pages to the class.

• Divide students in groups of two
• Choose a minimum value and a maximum value on the number line
• Select two numbers with a small difference as the target range

• Player one selects the operation (addition or subtraction), the start number, and a target range
• Player two uses mental arithmetic and estimation skills to choose a number that with the operation selected and the start number will form an expression whose answer lies in the target range
• If the answer does not fall in the target range, Player two chooses an operation (addition or subtraction) and passes the calculator to Player one
• The game continues until one of the players gets an expression whose answer lies in the target range
• Each group records the operation chosen, numbers entered, and the sum or difference values
• #### After the Activity

Review student results:

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