Transcript LCM, LCD, Compare Fractions

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The product of a whole number
multiplied by any other whole
number is called a multiple.
Name the first six multiples of 6
6, 12, 18, 24, 30, 36
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Name the first six multiples of 5
5, 10, 15, 20, 25, 30
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A Common Multiple is a number
that is a multiple of two numbers.
Here are common multiples for the
numbers 4 and 10
4 = 4, 8, 12, 16, 20, 24
10 = 10, 20, 30, 40, 50,
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LCM - Least Common Multiple is the smallest
number that a set of given numbers divides
evenly into.
LCM is also known as finding the Least
Common Denominator
It is useful to know how to do this so you
can find a common denominator when
adding or subtracting fractions.
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To find the LCM 4 and 12
1) List the multiples of both numbers
4 = 4, 8, 12, 16, 20…
LCM
is
12
12 = 12, 24, 36, 48…
2) Find the least multiple that both
numbers have in common.
This method is useful if both numbers are small.
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What is the LCM of 6 & 8?
6 = 6, 12, 18, 24, 30, 36
8 = 8, 16, 24, 32, 40, 48
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What is the LCM of 3 & 9?
3 = 3, 6, 9, 12, 15, 21,
9 = 9, 18, 27, 36, 45, 54
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Find the LCM of 10 and 12.
Make a List of Multiples
10 = 10, 20, 30, 40, 50, 60, 70, 80…
12 = 12, 24, 36, 48, 60, 72…
LCM = 60
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Find the LCM of 25 and 30.
Make a List of Multiples
25 = 25, 50, 75, 100, 125, 150, 175…
30 = 30, 60, 90, 120, 150, 180…
LCM = 150
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What is the LCM used for?
The LCM is used to find common
denominators so that fractions may be
easily compared, added, or subtracted.
15
24
GIANT ONE
3 5
3 8
 
>
GIANT ONE
7
2
12 2
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 
14
24
The Giant One is used to find equivalent fractions.
3

4
5
15

5
20
It is used to reduce or simplify fractions.
4

10
2
2

2
5
The giant one works because of the Identity Property.
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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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To compare fractions sometimes we use
inequality symbols rather than an equal sign.
> Means larger or greater than
< Means smaller or less than
= Means equal to
Large #
Small #
The hungry alligator eats the larger number.
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To compare fractions sometimes we use
inequality symbols rather than an equal sign.
> Means larger or greater than
< Means smaller or less than
= Means equal to
5
4
5 is greater than 4
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To compare fractions sometimes we use
inequality symbols rather than an equal sign.
> Means larger or greater than
< Means smaller or less than
= Means equal to
5
4
If this method confuses you…try this!
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<
ess than
reater than
Left hand
= Less than
5
>
4
If this method confuses you…try this!
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Which is greater?
LCM  60
28

60
 
4
4
7
15
>
9
20
 
3
3
27

60
7 is greater than 9
15
20
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Use < or > to compare the
fractions below.
28

35
 
7
7
4
5
>
 
5 5  25
35
7 5
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Use < or > to compare the
fractions below.
 
2 5
10
 2 8
16
>

9 1  9
16
16 1
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Use < or > to compare the
fractions below.
 
15 3 5
 3 12
36
<
 
4 4
16

9 4
36
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The GCF and LCM are used so regularly that
most people find them mentally.
GCF = 1
1)
8
GCF = 5
9
2)
LCM = 72
15
20
LCM = 60
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The GCF and LCM are used so regularly that
most people find them mentally.
GCF = 4
1)
12
GCF = 4
20
2)
LCM = 60
8
12
LCM = 24
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THE END!
Take out your
study guide.
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#6
TO FIND THE LCM OF 4 and 12:
1) List the multiples of both numbers
4 = 4, 8, 12, 16, 20…
12 = 12, 24, 36…
2) Find the least multiple that both
numbers have in common.
LCM is 12
Least Common Multiple is also known as LCD.
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#7
Comparing Fractions
Read these symbols from left to right.
< Less than
> Greater than
 Less than or equal to
 Greater than or equal to
****************************************************************
To compare fractions you must show your work!
 
6 8
48

6 10
60
>
 
9 5
45

12 5
60
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