Adding and Subtracting Fractions
This is the thing that might get
complicated. Don’t worry though, I
heard that your teacher is amazing
Let’s Get … Visual
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In the same way, we can add fractions
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2
Let’s get … Visual
What we need to know …
• When adding or subtracting fractions, ONLY
add or subtract the Numerator.
• REMINDER, in case the above rule wasn’t
clear: DO NOT TOUCH THE DENOMINATOR
• For example …
This is correct. Hip Hip Hooray.
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4
This is WRONG. Don’t be this guy
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8
Same thing for Subtraction. Good work
kids
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1
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Again, don’t do this. Seriously, who is
this guy?
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1
4
4
0
Now … for the tricky part.
• What if the denominators are different?!!
• Are we doomed? Are we in trouble? Oh the
humanity!!
Chill out, you’re fine. Like seriously,
relax
• It is called “Finding a Common Denominator”
• Remember that thing about Equivalent
Fractions and multiplying by one and all that
goodness? What about LCMs?
• Yeah, that is going to be super important for
this lesson.
Some things to Remember
• If the Denominators are not the same, YOU
CANNOT ADD OR SUBTRACT THEM
• But, there is a way to make them the same,
and that is multiplying that fraction by one 
• Aren’t we tricky?
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5
10
2x2
5x2
1
10
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10
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6
5
1
12
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9
1
14
7
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?
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2
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6
5
1
12
4
9
1
14
7
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8
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13
1
15
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13
1
15
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1
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13
1
15
10
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2
1
12
18
5
1
12
9
9
1
14
21
?
?
?
A thing about Denominators
• If worse comes to worst, just multiply the two
different denominators together.
• If you do this, you are not guaranteed a
LOWEST common denominator, but you are
guaranteed a COMMON denominator, which
is all that you actually need for adding and
subtracting fractions.