Transcript n) Add & Subtract Negative Fractions Unlike Denomin

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Parts of a Fraction
3
4
= the number of parts
= the total number of parts
that equal a whole
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Parts of a Fraction
3 = numerator
4 = denominator
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A Common Multiple is a
number that is a multiple of
two or more numbers.
Some multiples of 3 & 6
6, 12, 18, 24, 30, 36, 42
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The LCM is the smallest multiple
that two numbers have in
common.
5 = 5, 10, 15, 20, 25, 30
6 = 6, 12, 18, 24, 30, 36
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To Add or Subtract Fractions
With Unlike Denominators
List the multiples of each
denominator to find the LCM.
1
5 = 5, 10, 15, 20, 25, 30
1
+ 10 = 10, 20, 30, 40, 50
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To Add or Subtract Fractions
With Unlike Denominators
Compare your lists. Which multiples
do 5 and 10 have in common?
1
5 = 5, 10, 15, 20, 25, 30
1
+ 10 = 10, 20, 30, 40, 50
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To Add or Subtract Fractions
With Unlike Denominators
This number is also called the
least common denominator.
1
5 = 5, 10, 15, 20, 25, 30
1
+ 10 = 10, 20, 30, 40, 50
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SHORTCUT: Check to see if the smaller
denominator divides evenly into the larger
denominator. If it does, use the larger
denominator for your LCD or LCM.
1
5
1
+ 10
5 will divide evenly into 10,
so 10 is your denominator.
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Rewrite the fractions using the least
common denominator or least
common multiple.
1
5
1
+10
10
10
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Find the equivalent fractions for 1/5
& 1/10 with 10 as the denominator.
1
5
1
+10
10
1
10
You know that 1/10
is equal to 1/10 so
Put a 1 over the
Denominator of 10.
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Find the equivalent fractions for 1/5
& 1/10 with 10 as the denominator.
1
5
1
+10
10
1
10
To find the top
number, ask yourself
what do you multiply
the 5 by to get 10.
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Now just add the numerators.
1 x 2 =2
5 x 2 10
1
1
+10
10
Remember when
adding fractions
you never add the
denominators.
3
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Identity Property states that any number
multiplied by one equals itself
n 1  n
2
3
2
4

2
6
This is useful to know so you can find a
common denominator for adding and subtracting
fractions.
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1
2
-1
+8
8
8
Find a
Least Common
Denominator
(LCD).
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1x 4 = 4
2x 4 = 8
-1x 1 = -1
+ 8x 1 = 8
Now fill
in your
Giant Ones.
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1x 4 = 4
2x 4 = 8
-1x 1 = -1
+ 8x 1 = 8
3
8
Add numerators.
The denominator
stays the same.
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-2
5
1
+3
15
What is a good
denominator?
15
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-2
5 x 3 = 15
1
+ 3 x 5 =15
Ask yourself
what do you
multiply the
denominator
by to get 15.
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-2 x 3 = -6
5 x 3 = 15
1x 5 = 5
+ 3 x 5 =15
Fill in your
Giant Ones.
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-2 x 3 = -6
5 x 3 = 15
1x 5 = 5
+ 3 x 5 =15
-1
15
Add the
numerators.
The denominator
stays the same.
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-1 x 2 = -2
6 x 2 = 12
1x 3 =3
+ 4 x 3 =12
1
12
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5 x 4 = 20
6 x 4 = 24
1x 3 =3
- 8 x 3 =24
17
24
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-2x 3 = -6
3x 3 = 9
1x 1 =1
- 9x 1 =9
-7
9
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-6 – 1 =
-6 + -1 =
-2 x 2 = -4
4x 2 = 8
2x 1 =2
+ 8x 1 =8
-2
8
-4 + 2 = -2
=
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-1
4
-4 x 3 = -12
5 x 3 = 15 -12 – -10 =
-2 x 5 = -10
-12
+
+10
=
15
x
5
=
-3
-2
15
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REMEMBER:
To Always Show Your
Work and The Giant One!
Take out your study guide!!!
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#23
4x3=
5x3=
-2 x 5 =
+3 x5=
Add Fractions
12
15
-10
15
2
15
1) Find a common
denominator.
2) Add the numerators.
3) Keep the common
denominator the same.
4) Simplify or reduce.
Change improper
fractions to mixed #s.
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Add & Subtract Negative Fractions
#24
-2 x 2 = -4
6 x 2 = 12
3x 3 =9
+ 4 x 3 =12
5
12
-4 x 2 = -8
5 x 2 = 10
1x 1 = 1
- 10 x 1 = 10
-8 – 1 =
-9
-8 + -1 = -9
10
Extras
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4 x 3 = 12
5 x 3 = 15
2 x 5 = 10
+ 3 x 5 = 15
22
15
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Simplify Your
Answer
22
15
1
7
15
15) 22
15
7
ALWAYS SIMPLIFY YOUR
ANSWER IF YOUR ANSWER IS AN
IMPROPER FRACTION!
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-2x 3 = -6
3x 3 = 9
1x 1 =1
- 9x 1 =9
-7
9
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-6 – 1 =
-6 + -1 =
-6 + -1 = -7