Math Notes: Order of Operations (a.k.a. PEMDAS)

When you have a math problem with multiple operations (+,-,x,/) in the same problem, you MUST follow the order of operations. There is a well-known mnemonic device that parents and grandparents might even remember from their school days: Please Excuse My Dear Aunt Sally. Some people remember this as "PEMDAS." It stands for the order you should do your math operations:
Please = parentheses
Excuse = exponents
My = multiply*
Dear = divide*
Aunt = add*
Sally = subtract*

*What most students forget is that when you get to the multiply/divide operations, you must work from LEFT to RIGHT (so you could divide before you multiply). This also applies to the addition/subtraction operations. When you've done everything else, then you add and subtract from LEFT to RIGHT.

For example: Solve (7 x 9) - 5 x 4 + 7.
A. Start with the parentheses: (7 x 9) = 54
The problem is now 54 - 5 x 4 + 7.
B. Check for exponents. There are none so move on.
C. Multiply or divide from left to right. Since 5 x 4 is 20, the problem is now 54 - 20 + 7.
D. Add or subtract from left to right. 54 - 20 = 34. Add 7. The final answer is 41.