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Welcome to my math blog! The purpose of this blog is to help you stay informed about our learning and experiences that have taken place during our math class. I have also included links your child (and you) may want to use in order to supplement math learning in 5th grade.

Monday, September 11, 2017

Divisibility Rules and Prime Factorization

Bell Ringer:

Today we visited SET and tried our hand at finding the six sets:


Lesson Frame:

  • We will take notes about divisibility rules and prime factorization.
  • I will diagram finding the prime factors of 18.
Lesson


We began our lesson by adding the divisibility rules to our math journal.  I demonstrated using the divisibility rules by finding all of the factors of 12.

Next, we created a page in our journal where we could work on prime factorization.  I explained that prime factorization is just finding the prime numbers that are multiplied together to make the original number.  Next, I had them write down the first 6 prime numbers, which are invaluable to know:

2, 3, 5, 7, 11, 13

Then, we revisited the divisibility rules to find ALL factors of 48.  We did this because I wanted to demonstrate that you can use any set of factors of a number on a factor tree and your prime factorization will always come out the same.

I had someone determine which set we would begin with.  I explained that we never include the "1 x ___", because 1 is not a prime number.  When we finished we had discovered that the prime factorization of 48 is 2x2x2x2x3.  A second student chose another set, yet the prime factorization was still the same.  Finally a third student chose a third set, again, this set had the exact same factors!  Point made!

Close

To demonstrate understanding, I asked the students to diagram the prime factors of 18 using a factor tree.

Assignment

We finished our day, by completing a Fifth Grade Builder and working on Think Through Math.

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