PEMDAS

Order of Operations: Fractions, Evaluating, and Simplifying

(An archive problem of the week) Last time we looked at the subtle distinction between the order of operations, which defines the meaning of an expression, and properties that allow us to do something other than what an expression literally says. Here I want to look at one longer discussion that brings out these issues …

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Order of Operations: Subtle Distinctions

Some questions we have been asked about the order of operations go beyond the what and why, pondering the relationship of the conventions both to theoretical matters (properties of operations) and to practical matters (evaluating and simplifying expressions). We will see here an important distinction between meaning and processes. PEMDAS vs properties, I: Meaning vs. …

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Order of Operations: Why?

Having looked at what the order of operations convention means, another common question is, why is it what it is? We’ll look at some basic ideas here, focusing on why we need a convention at all, and why the one we have makes sense; then next time we’ll dig in a little deeper, examining some …

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Order of Operations: Neglected Details

The basic statement of the order of operations covers the five main operations (exponents, multiplication, division, addition, and subtraction). But what about other operations like square roots? How about trigonometric functions? And are operations at the same level always carried out left to right? Here are some questions about the details we don’t often mention. …

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Order of Operations: Common Misunderstandings

Last time I started a series looking at the Order of Operations from various perspectives. This time I want to consider several kinds of misunderstandings we often see. Multiplication before division? Here is a question from 2005 from a teacher, “WRW”: Confusion over Interpretation of PEMDAS In telling students to “do multiplication and division IN …

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Order of Operations: The Basics

The order of operations in algebra (also called operator precedence) is a very common source of questions; I count at least 50 archived discussions explicitly about the topic (not just mentioning it in passing), in addition to the Ask Dr. Math FAQ on the subject.  I’ll devote the next few posts to looking at various aspects …

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Why We Care About “Why”

(Archive question of the week) One day back in November, as I entered the community college where I teach, a man came in behind me with his son, probably about 3 years old. It was the first snowy day of the year, and the father stood on the mat wiping his feet, while the little …

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