Prime numbers and factors Prime numbers Prime numbers divide by themselves and one So 331or 13131 But 16 divides 161 and 82 and 44 So you see that prime numbers are very specific ID: 246370
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Slide1
In this presentation I will be explaining prime numbers, how to find prime factors of numbers and the Highest conmen factor and the lowest conmen multiple.
Prime numbers and factors.Slide2
Prime numbersPrime numbers divide by themselves and one.
So… 3=3*1…or… 13=13*1But 16 divides 16*1 and 8*2 and 4*4
So you see that prime numbers are very specific.
Just remember 2,3,5,7,11,17Slide3
Prime factorsPrime factors are factors of numbers like 108 that are prime.
For example: the factors of 108 are 2,2,3,3,3When you multiple all these numbers together you will get 108. Try it. Slide4
How to work out the prime factors of numbersWe can make it simple. Lets use a tree. If we put the number at the top… lets say 90.
We then work out all the factor of 90. just watch!
90
2
45
5
9
3
3
Now we highlight the prime numbers.
2
5
3
3Slide5
Your turn!Now you try these. Get some paper and draw trees.
54
136
60
90
21
2*3*3*3
2*2*2*17
2*2*3*5
2*3*3*5
3*7Slide6
HCF (Highest conmen factor)The highest conmen factor is found by using a V
enn diagram. A Venn diagrams looks like this.Slide7
You will be given two numbers that you will have to find the prime factors for. So find the prime factors for these two numbers.100 25Answers2*2*5*5 5*5Now look at the similar numbers. There are two fives in both the answers. So these go in the middle of the Venn diagram. You don’t repeat these numbers
5
5
2
2
100 25
To work out the HCF you need to multiple all the numbers in the middle of the Venn diagram.
So 5*5=25
The HCF =25Slide8
Your turnIf you get stuck click on the question mark at the top of the screen and watch the previous slide again.
54
136
60
21
HCF = 3
HCF= 4Slide9
LCM (lowest conmen multipleTo work out the LCM you do the same as the HCF but instead of multiplying the numbers in the middle of the Venn diagram you multiply all the numbers in the
Venn diagram.
5
5
2
2
100 25
2*2*5*5=100
LCM=100
You will find that the LCM is always bigger than the HCF.Slide10
Your turnIf you get stuck click on the question mark at the top of the screen and watch the previous slide again.
54
136
60
21
LCM=378
LCM=2040Slide11
Well done. Try the Homework on Mymaths.