NCTM Standards: Represent and analyze mathematical situations and structures using algebraic symbols; Understand patterns, relations and functions

Activity 2: Priming The Numbers

Added on 9/19/2007

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ACTIVITY OVERVIEW

In this activity we will:

  • Use the fraction function to find the prime factors of a number using the SIMP key automatically and by investigation

  
First, set your calculator so that it looks like the screen at the right. These settings will output your fractions as only fractions and will not simplify the fractions automatically.  Press  and your arrow keys to move to the settings and press  to select them. no alt text supplied
Enter a number as the numerator and denominator of a fraction. Enter the number, press the  key and enter the number again. Then press the  key.  You should see a screen similar to what is on the right.
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In order to find the prime factors of a number, press the key and press .  Each time you do this, the calculator will find the next smallest prime factor.  Again, you can see what the screen should look like on the right. 
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You will know that you have found ALL of the prime factors of a number when your fraction results in 1/1 and the arrow key next to your answer disappears.  The down arrow next to the output tells you that you have not found all of the prime factors of the original number. no alt text supplied

In order to test your answers, multiply together ALL of the prime factors of a number you have found.  What number should you get as an answer?


  
You can also find prime factors by entering them yourself.  Enter 36 as your numerator and denominator and then, press and enter a prime number you believe is a factor.  Then press . no alt text supplied
If your prime “guess” is included in the number, it will reduce the number by that factor.  If it is not a factor, the fraction will not change.
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Once you have practiced this, take turns with a partner to find the complete factorization of a number by entering all of the factors as simplifiers.  You will get 1/1 if your guess is complete and the arrow will disappear.
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