Greatest Common Factor (GCF)-The greatest common factor or GCF is the greatest factor that two or more numbers have in common. The greatest common factor of 16 and 20 is 4. To find this first list all the factors of each number:

16: 1, 2, 4, 8, 16

20: 1, 2, 4, 5, 10, 20

Then circle all the factors that the numbers have in common. The GCF is the greatest factor that the numbers have in common.

Exponents-You can use an exponent and a base to show repeated multiplication of the same factor. An exponent is a number that tells how many times a number called the base is used as a repeated factor. For example: 5 x 5 x 5 = 53

Numerical Expressions-A numerical expression is a mathematical phrase that uses only numbers and operation symbols. For example:

4 x (8 + 51). You evaluate a numerical expression when you find its value. To evaluate an expression with more than one operation, you must follow a set of rules called the order of operations. A way to remember these is Please Excuse My Dear Aunt Sally. (Parenthesis and Exponents, Multiplication and Division, Addition and Subtraction)

4 x (8 + 51) = 52