Math Help

Chapter 5 help:

Divisibility rules:

2- the number must be even

3- Add the digits of the number, and the sum must have 3 as a factor

5- The number must end in 0 or 5

6- The number must have both 2 and 3 as a factor

9- Add the digits of the number, and the sum must have 9 as a factor

10- The number must end in 0. 

A prime number does not have any other factors besides 1 and itself Ex. 3, 17, 2, 11, 5

A composite number has more than just the factors of 1 and itself Ex. 4, 56, 30, 9

To find the prime factorization of a number, you must complete a factor tree.  For help on creating a factor tree visit here: Make a Factor Tree  Once you have made the factor tree, the prime factors you have found together make the prime factorization. For example, for the factor tree of 36 you end up with 2x2x3x3 this would be: 22 x 32.

To find the GCF or Greatest Common Factor between two numbers, you can either make the factor trees of both numbers and multiple the prime numbers they have in common, or make a list of all the factors for both numbers and find the biggest factor they share.   Example:

  • 20= 1, 2, 4, 5, 10, 20
  • 24= 1, 2, 3, 4, 6, 8, 12, 24

The biggest factor these two numbers have in common is 4, therefore the GCF= 4.

**If you need help with long division, here is a site you can go to to see the step by step process. Otherwise, look in your book on page 744 in the skills review handbook section.

You can also always refer back to your key concepts section of your notebook where you keep example problems as a resource for yourself.