Autumn Half Term #1 - Types of Number, Prime Factor Trees, HCF and LCM (up to 3 numbers)

One of the topics covered in Autumn Half Term #1. Includes definitions of primes, factors, multiples, prime factorisation, HCF and LCM with three methods (basic, exam method; using prime factorisation and venn diagrams).

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Prime numbers - definition (with example)?
Prime numbers DON'T divide by anything EXCEPT 1 and itself
E.g. 11 is a prime no. as its only factors are 1 and 11
1 of 14
Prime numbers - usually end in (with example)?
They end in 1,3,7 or 9 ONLY
BUT - 1 ISN'T a prime number and NOT ALL numbers ending in 1,3,7 or 9 are prime number E.g. 9 - it's not a prime number as a factor of it is 3
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Prime numbers - how to find?
Does it end in 1,3,7,9?
Find its square root
List all the primes less than its prime root
Divide all of these by the number in question
If none of them divide cleanly into it the number is a prime number, if they do it ISN'T a prime number
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Multiples - definition (with example)?
The times table of a number
E.g. multiples of 4 are: 4, 8, 12, 16 etc
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Factors - definition (with example)?
All the numbers that divide into a number
E.g. factors of 10 are: 1, 10, 2, 5
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Product of primes/prime factorisation - how to find (with example)?
FACTOR TREE
Divide the number by prime numbers until you get prime factors and then circle the primes
E.g. prime factors of 420 are 2,2,3,5,7 - I would write it as 420=2x2x3x5x7
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HCF - definition (with example)?
Highest Common Factor - highest number that goes into both numbers.
E.g. 4 is the highest number that goes into both 8 and 12.
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LCM - definition (with example)?
Lowest Common Multiple - lowest number that both numbers go into.
E.g. 24 is the lowest number that 8 and 12 both go into.
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HCF - Method 1?
BASIC
1. List all of the factors of all the number
2. Find the biggest in all the lists
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LCM - Method 1?
BASIC
1. List multiples of all the numbers
2. Find the smallest one that is a multiple of all the numbers
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HCF - Method 2 (with example)?
EXAM METHOD
1. Prime factorisation e.g. 36 and 45. 36 = 2² x 3². 45 = 3² × 5
2. HCF - whatever is in common, which is 3² = 9
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LCM - Method 2 (with example)?
EXAM METHOD
1. Same as HCF
2. LCM - whatever is left, which is 2² x 3² x 5 (only one of the 3²'s were cancelled out) = 180
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HCF - Method 3?
VENN DIAGRAM
1. Draw a venn diagram and label each circle for each of your original numbers
2. Place numbers that appear in both multiplications in the overlap
3. Put the other numbers in the correct circles.
4. HCF = multiply all of the numbers in the ov
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LCM - Method 3?
VENN DIAGRAM
1. Same as HCF
2. LCM - multiply all the numbers in the venn diagram
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Other cards in this set

Card 2

Front

Prime numbers - usually end in (with example)?

Back

They end in 1,3,7 or 9 ONLY
BUT - 1 ISN'T a prime number and NOT ALL numbers ending in 1,3,7 or 9 are prime number E.g. 9 - it's not a prime number as a factor of it is 3

Card 3

Front

Prime numbers - how to find?

Back

Preview of the front of card 3

Card 4

Front

Multiples - definition (with example)?

Back

Preview of the front of card 4

Card 5

Front

Factors - definition (with example)?

Back

Preview of the front of card 5
View more cards

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