Divisibility Rules are important because...

• They are shortcuts to help you tell when a number can be divided by another number evenly (with NO remainder)

• They help with factoring large numbers (finding Prime Factorization or the GCF)

• They help when simplifying fractions or ratios

• A prime number is a whole number greater than 1 that has ONLY 2 FACTORS--1 and itself. 

• A composite number is a whole number greater than 1 that has more than 2 factors.

• Remember: 1 is neither prime NOR composite!

• Prime Factorization--the way of writing a number as the multiple of their prime factor

Factors--numbers you can multiply together to get another number

Greatest Common Factor--the biggest factor that 2 or more numbers share.

You can use 2 methods to find the GCF:

1. Listing the factors for each number (Rainbow Method)

2. Factor Tree Method

Multiples--the result of multiplying 2 numbers together

Least Common Multiple--the smallest multiple that 2 or more numbers share

To find the LCM, list the multiples for each number (in order!). The first one they have in common is the LCM!