directed numbers
Post on 08-Jul-2015
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Directed Numbers
Objective: Be able to add and subtract directed numbers.
First, you have to know the number line!
If you remember what the number line looks like you will find this easy!
87654321
-1-2-3-4-5-6-7-8-9
0
Let’s look at a question
Work out
+6 + -3What does this mean?
The first part tells you where to start on the number line.
The symbols tell you what to do.
If they are the same, you add.
If they are different, you subtract
The last number tells you by how much.
Let’s do it
+6 + -3
87654321
-1-2-3-4-5-6-7-8-9
0
Start here
They are different, so subtract… … this
much
One!Two!Three!
So there’s your
answer, 3
+6 + -3 = 3
Here’s another …
-4 - -9
87654321
-1-2-3-4-5-6-7-8-9
0
Start here
They are the same, so we add… … this
much So there’s your
answer, 5
Here’s another …
-4 - -9
87654321
-1-2-3-4-5-6-7-8-9
0
Start here
They are the same, so we add… … this
much So there’s your
answer, 5
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