Tuesday, November 3, 2009

Prime Factorization

Today in Pre-Algebra we studied Prime Factorization. I use a method that I picked up from another teacher at the Kauffman Foundation a couple of years ago. It is so much better than using factor trees! When giving students a choice between factor trees or this method, students always select the method I am going to share with you here. This method is so awesome it should be used in all math books! It is great for struggling learners...but even my advanced math students prefer it. I call it Prime Factorization using the Composite/Prime Line. I like the fact that it uses the vocabulary words composite and prime...two words that they need to know for state assessments! Here is how it works...

Let's say you have the # 48. You start by drawing a vertical line down your paper. Composite numbers go on the left side of the line, and prime numbers go on the right side. 48 is a composite number so it goes on the left side. Since it is an even number, students know that the prime number 2 will go into it. Place the number 2 (a prime number) on the right side of the vertical line- then take 2 into 48- it goes into 48, 24 times. Twenty-four is a composite number, so it will be on the left side of the composite/prime line. Keep going until you have taken the number down to only it's prime factors.

The Prime Factorization for 48= 2^4 * 3. Is this cool or what? No longer do my students loose one of the prime factors in the branches of the factor tree!

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