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What Does PEMDAS Mean, and Why Does It Matter?

what does PEMDAS stand for: Colored blocks with mathematical symbols on top of a wooden surface

You may have heard the phrase, "Please excuse my dear Aunt Sally," (PEMDAS) in math class. But what does PEMDAS stand for, how does it relate to the order of operations, and how does it help solve math problems with multiple mathematical expressions?

PEMDAS Is an Acronym for the Order of Operations

When you take the letters in the mnemonic device, "Please excuse my dear Aunt Sally" (or "purple eggplants make delicious afternoon snacks"), you get PEMDAS. Each letter represents an operation in math:

P: Parentheses

E: Exponents

M: Multiplication

D: Division

A: Addition

S: Subtraction

When doing order of operations, the order of the letters in PEMDAS tells you in what order you should complete mathematical expressions. Evaluating a set of parentheses always comes first. Next, compute any exponents. Then, move onto multiplication and division. Finally, finish with addition and subtraction.

Why Is the Order of Operations Important?

The order in which you calculate your operations will determine whether you find the correct answer to a complex mathematical expression. Let's take even a simple example:

what does PEMDAS stand for: Simple mathematical expression

According to PEMDAS, you should do the multiplication first:

what does PEMDAS stand for: Solution of a mathematical expression according to PEMDAS

However, if you choose to do the addition first, you get a different and incorrect answer:

Simple mathematical expression

Simple mathematical expression

Simple mathematical expression

The PEMDAS rule helps you from arriving at the wrong answer if you mix up the order of parentheses, exponents, multiplication and division, and addition and subtraction.

What Does PEMDAS Stand for?

PEMDAS is a great acronym to help you memorize the order of operations. You can use the common mnemonic "Please excuse my dear Aunt Sally" or even come up with your own phrase as part of your studying.

When you remember that parentheses come before exponents, which come before multiplication and division, which comes before addition and subtraction, you’ll be on the right track to getting the right answer any time you apply that set of rules to a problem.

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