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### Course: Operations and Algebraic Thinking 189-200>Unit 5

Lesson 1: 2-step expressions

# Order of operations (2-step expressions)

Sal evaluates 2-step whole number expressions with different operations.

## Want to join the conversation?

• there are questions that i get wrong because i choose to do multiplication before division why is that?
shouldn't i be following PEMDAS?
• PEMDAS does not mean multiplication before division, even though it might appear that way. These two operations have equal priority and so should be done left to right. PEMDAS should really be presented as P E MD AS.
• One of the questions was 9-1+9+3 to the 4th power.
According to PEMDAS, I did:
9-1+9+81 (exponents first)
1+9=10 and 10+81=91 (addition next since no mult. or div.)
but it was supposed to be 98.
How do we decide when we're supposed to do A & D from left to right and when we're supposed to follow PEMDAS?!
• It is really PE (MD) (AS) because multiplication and division are on same level and addition and subtraction is on the same level, so these go from left to right
• How about someone says, "What is 2 divided 6 times 7". What do you do first?
• Multiplication and Division are equal operators and should be performed left to right.

So, you would perform 2/6 first, then multiply that result by 7.
• how is a square a rectangle
• A rectangle is a shape made of four sides with 90° angles at each corner. A square is a special kind of triangle where all the sides are equal. All squares are triangles, but not all rectangles are squares. Hope this helps!
• I watched it twice but I still don't understand why
5-3+2 is doing the - first, then the +, but doing the + first gives a different result. Did I miss an explanation? I only caught that multiplication or division is done before addition or subtraction, but not which of each is done first?
• it is because 5-3=2 +2=4 and 3+2=5 -5=0! multiplication is first as well as addition

whenever you're stuck, just remember PEMDAS parentheses, exponents, multiplication, division, addition, subtraction

(1 vote)
• can you learn math in any age
• yes I guess
• Why do we not use the PEMDAS order of operations?
• All the examples in this video do use PEMDAS. I'm going to assume that the probelm you find confusing is the: 5-3+2 where Sal subtracts as the first step. You may not realize the "AS" are one group. You should work them left to right. This is why Sal does the subtraction then the addition.

Note: "MD" is also one group and should be done from left to right.

Hope this helps.
• like just put them into each other