Find the Lowest Common Denominator

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Question 1 of 5

1. Question
Find the Lowest Common Denominator ( $LCD$ ) between the numbers:

$5 & 8$
- (40)
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The Lowest Common Denominator (LCD) is the lowest number that is a multiple of both said numbers.

Method One

Start by listing out the multiples of each number

Multiples of $5$ :

$5\;\;10\;\;15\;\;20\;\;25\;\;30\;\;35\;\;40\;\;45$

Multiples of $8$ :

$8\;\;16\;\;24\;\;32\;\;40\;\;48$

Identify the smallest number that is both a multiple of $5$ and $8$

Multiples of $5$ :

$5\;\;10\;\;15\;\;20\;\;25\;\;30\;\;35\;\;\color{#CC0000}{40}\;\;45$

Multiples of $8$ :

$8\;\;16\;\;24\;\;32\;\;\color{#CC0000}{40}\;\;48$

The LCD of $5$ and $8$ is $40$

$40$

Method Two

Multiply the two numbers

$5xx8$ $=$ $40$

The LCD of $5$ and $8$ is $40$

Note that at times, this method will give out the highest common denominator. So, Method One is more accurate.

$40$
Question 2 of 5

2. Question
Find the Lowest Common Denominator ( $LCD$ ) between the numbers:

$8 & 4$
- (8)
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The Lowest Common Denominator (LCD) is the lowest number that is a multiple of both said numbers.

Start by listing out the multiples of each number

Multiples of $8$ :

$8\;\;16\;\;24\;\;32$

Multiples of $4$ :

$4\;\;8\;\;12\;\;16$

Identify the smallest number that is both a multiple of $8$ and $4$

Multiples of $8$ :

$\color{#CC0000}{8}\;\;16\;\;24\;\;32$

Multiples of $4$ :

$4\;\;\color{#CC0000}{8}\;\;12\;\;16$

The LCD of $8$ and $4$ is $8$

$8$
Question 3 of 5

3. Question
Find the Lowest Common Denominator ( $LCD$ ) between the numbers:

$3 & 21$
- (21)
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The Lowest Common Denominator (LCD) is the lowest number that is a multiple of both said numbers.

Start by listing out the multiples of each number

Multiples of $3$ :

$3\;\;6\;\;9\;\;12\;\;15\;\;16\;\;18\;\;21$

Multiples of $21$ :

$21\;\;42\;\;63$

Identify the smallest number that is both a multiple of $3$ and $21$

Multiples of $3$ :

$3\;\;6\;\;9\;\;12\;\;15\;\;16\;\;18\;\;\color{#CC0000}{21}$

Multiples of $21$ :

$\color{#CC0000}{21}\;\;42\;\;63$

The LCD of $3$ and $21$ is $21$

$21$
Question 4 of 5

4. Question
Find the Lowest Common Denominator ( $LCD$ ) between the numbers:

$4 & 10$
- (20)
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The Lowest Common Denominator (LCD) is the lowest number that is a multiple of both said numbers.

Start by listing out the multiples of each number

Multiples of $4$ :

$4\;\;8\;\;12\;\;16\;\;20\;\;24$

Multiples of $10$ :

$10\;\;20\;\;30$

Identify the smallest number that is both a multiple of $4$ and $10$

Multiples of $4$ :

$4\;\;8\;\;12\;\;16\;\;\color{#CC0000}{20}\;\;24$

Multiples of $10$ :

$10\;\;\color{#CC0000}{20}\;\;30$

The LCD of $4$ and $10$ is $20$

$20$
Question 5 of 5

5. Question
Find the Lowest Common Denominator ( $LCD$ ) between the numbers:

$6 & 7$
- (42)
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The Lowest Common Denominator (LCD) is the lowest number that is a multiple of both said numbers.

Start by listing out the multiples of each number

Multiples of $6$ :

$6\;\;12\;\;18\;\;24\;\;30\;\;36\;\;42\;\;48$

Multiples of $7$ :

$7\;\;14\;\;21\;\;28\;\;35\;\;42\;\;49$

Identify the smallest number that is both a multiple of $6$ and $7$

Multiples of $6$ :

$6\;\;12\;\;18\;\;24\;\;30\;\;36\;\;\color{#CC0000}{42}\;\;48$

Multiples of $7$ :

$7\;\;14\;\;21\;\;28\;\;35\;\;\color{#CC0000}{42}\;\;49$

The LCD of $6$ and $7$ is $42$

$42$

Find the Lowest Common Denominator

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