Session 2 post: PEMDAS

Parentheses

Exponents

Multiplication

Division

Addition

Subtraction 

I remember this acronym well from school. But it always confused me: Do I follow PEMDAS within the parentheses? Am I supposed to work left to right? 

I headed over to Khan Academy and watched an introductory video. (Oh, yeah! PEMDAS is also known as the order of operations!)

The first thing I learned that I didn't remember was that Multiplication and Division are at the same level--it's NOT multiplication first, then division; instead, you work left to right. Same thing with Addition and Subtraction. So I'm rewriting this acronym:

Parentheses

Exponents

Multiplication/Division

Addition/Subtraction

Although I got the answer right on my first test question even though I treated MDAS as all separate items. Hmmm. Someone in the comments had that experience, too, it turns out. That commenter said sometimes it will work and sometimes it won't, depending on the problem. And the lesson added that if you have ALL addition or ALL multiplication in a problem, you don't have to worry about what order you do them in.

Time to practice:

Problem 1

Problem 2

Problem 3

Problem 4

Problem 5

Problem 6

Problem 7

Problem 8

NAILED IT!

That wasn't so bad. . . . 

I love this site so far, by the way. I went to the Common Core website mentioned in the instructions for the PLP, and a search for PEMDAS brought up no results. But at the top of each question on KhanAcademy, it had the Common Core standard at the top. And it turns out that order of operations is taught in sixth grade:

6.EE.A.2c

Evaluate expressions at specific values of their variables. Include expressions that arise from formulas used in real-world problems. Perform arithmetic operations, including those involving whole-number exponents, in the conventional order when there are no parentheses to specify a particular order (Order of Operations).

Khan Academy's layout of the Common Core standards is so much easier to read than the other site's!

Next week: Geometry.