Pre Algebra Order of Operations
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Order! Order!
Order of Operations

 
 Say you had a problem like this:
 

3 + 4 6

 
 before you say 42, you need to know a special rule:
 

 MULTIPLICATION GETS DONE

 BEFORE ADDITION

 
 That means first we multiply:
 

 4 6 = 24

 
 Then we add:
 

 3 + 24 = 27

 
 OK, Fine. Do x before +.
 
 Are there any other things like that to remember?
 
 A few:
 

 MULTIPLICATION GETS DONE

BEFORE SUBTRACTION 

 
 So if we have:
 

 2 6 - 3

 
 First we multiply:

 

 2 6 = 12

 
 Then we subtract
 

 12 - 3 = 9

 

 

 DIVISION GETS DONE

 BEFORE ADDITION

 
 So if we have:
 

 3 + 10 2

 
 First we divide:
 

 10 2 = 5

 
 Then we add:
 

 3 + 5 = 8

 

 

 DIVISION GETS DONE

 BEFORE SUBTRACTION

 
 So if we have:
 

 6 3 - 2

 
 First we divide:
 

 6 3 = 2

 
 Then we subtract:
 

 2 - 2 = 0

 
 Think of multiplication and Division as the big shots. 
 They go first. 
 
 Addition and subtraction follow along after.
 
 Swell. Let's put that all together in one sentence:
 

 MULTIPLICATION AND DIVISION

COME BEFORE 
ADDITION AND SUBTRACTION. 
 

 
 OK, That's fine. But what do we do with this puppy?
 

 2 6 4

 
 Multiplication and Division are equal big shots. 
 Which goes first?
 
 The rule for stuff like this says:
 

 WHEN YOU HAVE SIGNS OF EQUAL IMPORTANCE,

 GO LEFT TO RIGHT

 
 So we do
 

 2 6 = 12

 
 Then we do:
 

 12 4 = 3

 
 Addition and subtraction work the same way. 
 Just go left to right.
 
 Example:
 

 2 - 6 + 5

 
 First subtract:
 

 2 - 6 = - 4

 (oh no! not a negative number!)

 
 Then add:
 

 - 4 + 5 = 1

 
 Now let's do a nasty one.
 
 Example:
 

 3 5 - 2 + 4 - 6 2

 
 The multiplication and division get done first:
 

 3 5 = 15

 

 - 6  2 = - 3

 (remember, the signs are different so the answer is negative)

 
 Now the problem looks like this:
 

 15 - 2 + 4 - 3

 
 What's left is all addition and subtraction so just go left to right:
 

 15 - 2 = 13

 

 13 + 4 = 17

 

 17 - 3 = 14

 

   copyright 2005 Bruce Kirkpatrick

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