Mental Math
Mental Math is the study of doing arithmetic in your head. Not to be confused with Number Theory.
Contents
Summary
Mental Math is the study of mentally doing arithmetic, such as addition, multiplication, subtraction, or division. Mental Math also includes numerical tricks and memorization. Note, Mental Math is not the same as Arithmetic, which is the study of operating with real numbers. A Mental Math test is included in MATHCOUNTS and Math League as Number Sense.
Introduction
Arithmetic
The basic starting point of Mental Math is being able to know Arithmetic, the study of operating with real numbers without unknowns. Arithmetic consists of a basic set of operations:
- Multiplication
- Division
- Addition
- Subtraction
- Exponentiating
So the following problem would be considered arithmetic:
And this would not:
PEMDAS
PEMDAS is the common acronym for Order of Operations. Each letters stands for an operation: Parenthesis, Exponent, Multiplication, Division, Addition, Subtraction. Other names for Order of Operations are "Please Excuse My Dear Aunt Sally".
Example of use: 
If you follow PEMDAS, this should be your answer: 
