Education Technology

Somewhere In Between

Published on 01/08/2010

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.

Follow the Activity procedures:

  • 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