What Is the PEMDAS Rule?


Quick Answer

The PEMDAS rule determines which mathematical operations take precedence in a complex equation. The acronym stands for "Parentheses, Exponents, Multiplication, Division, Addition and Subtraction." Following the rule, students should resolve any parts of the equation in parentheses before then handling exponents and roots. Students then perform any multiplication and division before finally resolving any addition and subtraction portions of the equation.

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Full Answer

PEMDAS is necessary because there could be multiple ways to resolve a mathematical equation depending on a student's interpretation. "Four times two plus three" equals 11 if a student multiplies four and two and then adds three. It equals 20 if a student adds two plus three and then multiplies the sum by four. Using the PEMDAS rule, the first answer is correct, and the student should resolve the multiplication portion of the equation first before moving on to the subtraction.

While there are six letters in PEMDAS, the acronym only represents four steps in the mathematical process. After parentheses and exponents are handled separately, multiplication and division are their own step, and addition and subtraction are their own step. Multiplication and division can be applied simultaneously since the ultimate results are the same either way, and the same is true for addition and subtraction.

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