This particular lesson is an important starting point for fractions. Knowing the factors and multiples of a number is very useful when you need to cancel down a fraction or bring fractions to a common denominator.
• What are factors
• How to find factors
• Divisibility rules
• What are multiples
• How to find multiples
Key words: factors, multiples, division rules,
What are the factors?
The factors of a number are all the numbers that divide into it
Imagine factors as all ingredients used to build the number:
Take the example above:
In order to build 75 we need do multiply 3, 2 and 5
To find out the factors of as number we need to divide the number applying the divisibility rules:
Dividing by 2: All even numbers are divisible by 2.
Example: all numbers ending in 0,2,4,6
Dividing by 3: Add up all the digits in the number and find out what the sum is. If the sum is divisible by 3, so is the number.
Example: 12123 (1+2+1+2+3=9) 9 is divisible by 3, therefore 12123 is too!
Dividing by 4: See if the last two digits in your number are divisible by 4.
Example: 358912 ends in 12 which is divisible by 4, thus so is 358912.
Dividing by 5: Numbers ending in a 5 or a 0 are always divisible by 5.
Example: 25, 65, 200,
Dividing by 6: If the Number is divisible by 2 and 3 it is divisible by 6 also.
Example: 66; 30, 42
Dividing by 8: if the last 3 digits are divisible by 8, so is the entire number.
Example: 6008 – The last 3 digits are divisible by 8, therefore, so is 6008.
Dividing by 9: Almost the same rule and dividing by 3. Add up all the digits in the number, if the sum is divisible by 9, so is the number.
Example: 43785 (4+3+7+8+5=27) 27 is divisible by 9, therefore 43785 is too!
Dividing by 10: If the number ends in a 0, it is divisible by 10.
Example: 10, 100, 1000,
Finding the factors of a number
Just apply the divisibility rules using any of the next schemes above:
Multiples of a number
The concept of Multiple is the opposite to that of a
factor. If some number A is a factor of a number B, that
means that B is a multiple of A.
Any number has a set of multiples. These multiples are
that number multiplied by various integers. A number can
have infinity of multiples.
The multiples of 3 are it’s time tables
Some multiples of 12 : 24, 36, 48, 60
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