Prime factors?

Question

I've been asked to to find the prime factors of
18,
28,
20,
36,
42,
100,
45,
60,
30.
What are they and how do you work these out/ can't make head of tails of method. Can any of you experts help pls?

Answer 1

Prime number is the number that cannot be divided by anything other then 1 or itself. The first 12 prime are numbers: 1, 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31- for purpose of your problem you do not need to go more then that.

the way you try to find the prime factors - divide the number by 2 first. If you cannot (w/o the remainder), then try by 3. If you cannot, try 5, etc. Then, take each of the numbers that is left and divide it by another prime number - the smallest number that gives you a zero remainder. Keep going until you only have the prime numbers left
Let's start with 18. Can you divide it by 2? - yes: 18 = 2*9. Then, take 9 and see if you can divide it by 2? no. By 3? yes. So, 18 = 2*3*3.
28 = 2*14 = 2*2*7
20 = 2*10 = 2*2*5
36 = 2*18 = 2*2*9 = 2*2*3*3
42 = 2*21 = 2*3*7
100 = 2*50 = 2*2*25 = 2*2*5*5
45 = 3*15 = 3*3*5
60 = 2*30 = 2*2*15 = 2*2*3*5
30 = 2*15 = 2*3*15
Makes sense?

Answer 2

I shall explain you with a number 60 and then you can follow the same. I shall provide prime factor of all of them as well.
(18 = 2*3*3
28 = 2*2* 7
20 = 2* 2 * 5
36 = 2*2* 3*3
42 = 2*3 *7
100 = 2*2*5*5
45 = 3*3*5
30 = 2*3*5)

A number is prime if it does not have a factor smaller than it(except .1). that is it cannot be factored
60 = 2* 30
now 30 = 2* 15.
15 = 3 * 5 and these cannot be reduced
so 60 = 2* 2* 3 *5

Answer 3

Prime factors of a number are numbers are not divisible any other numbers than 1 and itself. Note that 1 is not considered a prime factor.

Example: the prime factors of 15 are 3 and 5 because 3 both 3 and 5 are prime.

Answer 4

Prime number are numbers that divide by only themselves and 1. If you do not know that then I can assume only 2 things, the teachers in the UK are worse than down here or you weren't paying attention in class. If it's the first, Blair should quit right now, if it's the second then you better wake up. The first 3 primes no.s except 1 are 2,3 and 5. The rest put your head to work. By the way, Shouldn't you be at school?

Answer 5

First you find the factors of each number.
Factors are numbers we multiply.

18....1 times 18
2 times 9
3 times 6.

So out of these factors, which are prime or composite.

1 is always NEITHER.

2 and 3 are PRIME (It's only factors are 1 and itself. In another words, the only way to multiply and make these numbers, is one time itself.)
6, 9, and 18 are COMPOSITE (6 is composite because of 2x3; 9 is composite because of 3x3; 18 is obviously composite because it has more than two factors listed.

If you need more help with the other numbers, go the site below. It lists EVERYTHING for you.

Answer 6

well you divide a number by a prime number that goes in to it, then you divide the answer by another prime number that can go in to that, you repeat this until the answer you get is a prime number. The prime factors are all the prime numbers that you needed to divide the beginning number with, and the prime number that you end with. If you times all the prime factors together, they will equal your first number. for example: 42.

42 divided by 2
=21
21 divided by 3
=7
7 is a prime number
therefore the prime factors of 42 are 2,3 and 7
2*3*7=42

example 2: 100

100 divided by 2
=50
50 divided by 2
=25
25 divided by 5
=5
5 is a prime number
2*2*5*5

if the question asks you to write this in index form this means that you simplify it to its powers so if you had 3*3*3 you'd write it as 3cubed

therefore, if you are asked to work out the prime factors of 100 and write them in index formyou should write 2squared*5squared

Answer 7

18 = 2*9 = 2*3*3 All primes
28 = 7*4 = 7*2*2
20 = 4*5 = 2*2*5
36 = 6*6 = 2*3*2*3
42 = 7*6 = 7*2*3
100 = 10*10 = 2*5*2*5
45 = 9*5 = 3*3*5
60 = 12*5 = 3*4*5 = 3*2*2*5
30 = 6*5 = 2*3*5

Answer 8

Prime numbers in the range you need are 2,3,5,7.
If a number is even, it is divisible by 2.
If the sum of the digits of a number is divisible by 3, the number is divisible by 3.
If it ends in 5 or 10, it is divisible by 5
a number is divisible by 7 if 2times the last digit subtracted from the rest of the number with the last digit cut off is divisible by 7. (the process can be repeated until you have manageable numbers to work with. Have fun!

Answer 9

prime factors means breaking a number into its prime factors{prime numbers}
prime numbers are those numbers divisible by itself and one.
example- 5 can be divided by 5 and 1, so its a prime number.
prime numbers [1-50]- 2,3,5,7,11,13,17,19,23,29,31,37,41,43,47.
here are the prime factors--
18-3,3,2
28-7,2,2
20--2,2,5
36--3,3,2,2
42--7,3,2
100--5,5,2,2
45--5,3,3
60--3,5,2,2
30--3,5,2