Activity 8: Keep The Change

October 31, 2007 through November 7, 2007

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ACTIVITY OVERVIEW

In this activity we will:

  • Develop strategies for subtracting a decimal from a whole number
  • Use the Number Line application to find strategies

Note: You will need the Number Line App for this activity.

  
When you go to the store and pay for an item, do you know how much change you will get? You will try to develop a method using the Number Line application. no alt text supplied
On your calculator, press the  key, select the number line app and press . Press any key and then select the fraction line option and again press . no alt text supplied
IN order to set up the window for our activity, press the  key.  Set up the line by entering these numbers and selecting these settings. Use the up or down arrow keys to get to each line. no alt text supplied
When you are done, press the down arrow key until you reach the last part of the window settings and make these settings as seen on the right. no alt text supplied
Press the  key to get to the fraction line. Think if a problem where you would subtract a decimal less than one from 1. Use your lower indicator to move it to the tenth closest to the answer you expect. Move the indicator to the upper indicator by using the up arrow.
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Then press  and enter 1 minus the decimal you were considering. How close is your estimate to the answer? no alt text supplied
Do you see a relationship between your guess and the problem? Can you come up with a method to calculate these answers mentally? Are their cases that won’t work? You may need to do this several times before you come up with a method that you feel works.
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Don’t forget to enter your guess on the lower indicator and then do the problem on the upper indicator.


  

You can move your upper indicator to different maximum values.  Make these whole numbers since you will usually pay with whole numbers of dollars.


 

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