What is a prime number? - By tecmath
Transcript
| 00:0-1 | Hello . Welcome to this video series . Looking at | |
| 00:01 | indices and crimes in this particular video . What we're | |
| 00:04 | going to be having a look at his prime numbers | |
| 00:05 | and composite numbers . So let's start with a definition | |
| 00:10 | . A prime number is accounting number that has exactly | |
| 00:13 | two factors itself and one accounting number by the way | |
| 00:16 | , these are just numbers 123456 numbers that you count | |
| 00:21 | with . So let's have a look at a couple | |
| 00:23 | of examples here of some prime numbers . So the | |
| 00:25 | number three is a prime number . And what makes | |
| 00:28 | three a prime number is while the only numbers that | |
| 00:31 | go into three or three and one . Okay because | |
| 00:36 | three times one is three but no other numbers go | |
| 00:38 | into three . So this makes three a prime number | |
| 00:41 | . Another example of a prime number is seven . | |
| 00:44 | Okay . Because the only numbers are going to seven | |
| 00:46 | A seven and one . So another prime number is | |
| 00:50 | two and two is a pretty special prime number because | |
| 00:53 | it's the only even prime number . The only factors | |
| 00:56 | are going to to to and itself and this makes | |
| 00:59 | it into a prime number . But you got to | |
| 01:01 | think for every other number well themselves and one will | |
| 01:05 | go into it . But also the number two of | |
| 01:07 | it's an even number will go into it . So | |
| 01:09 | too is the only even number that is a prime | |
| 01:11 | number . And you'll see this in a second when | |
| 01:13 | we have a look at composite numbers . In fact | |
| 01:15 | , let's have a look at composite numbers right now | |
| 01:18 | . So let's now have a look at composite numbers | |
| 01:21 | . A composite number is a number that has more | |
| 01:23 | than two factors . An example of this is six | |
| 01:27 | . Six is a composite number because it has the | |
| 01:29 | following factors . The numbers one and six going to | |
| 01:33 | 61 times six is equal to six . But we | |
| 01:36 | also have two other numbers are going to six which | |
| 01:38 | are two and three because two times three is also | |
| 01:42 | equal to six . So because six has four factors | |
| 01:46 | six is a composite number . You can also look | |
| 01:49 | at it as I was saying before six is an | |
| 01:51 | even number . That's not too . And we straight | |
| 01:53 | away . No , that it too is going to | |
| 01:55 | go into it . So we can also know that | |
| 01:57 | little clue there , that six is going to be | |
| 01:59 | a composite number . What about we have a look | |
| 02:02 | at another example . What about the example of 15 | |
| 02:06 | ? They're 15 is a composite number . It has | |
| 02:08 | the following factors one and 15 But the other numbers | |
| 02:12 | are going to 15 are three and 5 Because it | |
| 02:17 | has more than two factors . 15 is also a | |
| 02:19 | composite number . And just a little hint here when | |
| 02:22 | you're looking to see whether a number is prime or | |
| 02:24 | composite apart from also just being an even number that's | |
| 02:27 | not too You can look for this little clue if | |
| 02:29 | the number finishes in a five or a zero and | |
| 02:32 | the number is not five because five is a prime | |
| 02:35 | number . But we also know that any number that | |
| 02:38 | is divisible by five ends in a five or a | |
| 02:41 | zero . So it's a good little clue for looking | |
| 02:44 | for composite numbers . If the number finishes in a | |
| 02:46 | five or a zero and the number is not five | |
| 02:48 | , it's going to be a composite number . So | |
| 02:50 | now let's have a look at a couple of examples | |
| 02:53 | . Are these following numbers prime or composite ? So | |
| 02:55 | let's have The first number . Is 11 . Is | |
| 02:58 | it a prime number or a composite number ? So | |
| 03:01 | what factors does 11 have 11 has the following factors | |
| 03:04 | one And 11 ? Because it only has two factors | |
| 03:09 | it's going to make 11 a prime number . Hopefully | |
| 03:13 | you got that right . What about another example ? | |
| 03:16 | What about the No ? 12 ? Okay . What | |
| 03:20 | factors does 12 have ? So 12 has a whole | |
| 03:23 | bunch of factors and you probably think of these really | |
| 03:25 | quickly . We have one And 12 . But you | |
| 03:28 | also have the numbers two and six because two times | |
| 03:32 | six is equal to 12 . But we also have | |
| 03:34 | the numbers three and four . So we know that | |
| 03:38 | 12 is a composite number . The other thing which | |
| 03:41 | might have given this away is because 12 is an | |
| 03:43 | even number . That's not too . We also could | |
| 03:46 | have said pretty much straight away that 12 was a | |
| 03:48 | composite number . What about one last example ? What | |
| 03:52 | about a really hard example now , what about we | |
| 03:54 | go the following number 1032 . Is that a prime | |
| 03:59 | number or a composite number ? So you can look | |
| 04:02 | at this straight away and say , well , we | |
| 04:04 | know that this is a composite number and what tells | |
| 04:06 | us this without working at any of the factors . | |
| 04:08 | Because it finishes in her too . We know that | |
| 04:11 | this number is going to be a composite number without | |
| 04:15 | doing any calculations here , because 1,032 will go into | |
| 04:19 | it and 2 516 will go into it without doing | |
| 04:24 | any other factor trees or anything like this . We | |
| 04:28 | know that this number is indeed composite . So hopefully | |
| 04:31 | you're gonna be okay with these sorts of numbers here | |
| 04:34 | anyway , we'll see you next time . Bye . |
Summarizer
DESCRIPTION:
OVERVIEW:
What is a prime number? is a free educational video by tecmath.
This page not only allows students and teachers view What is a prime number? videos but also find engaging Sample Questions, Apps, Pins, Worksheets, Books related to the following topics.
GRADES:
STANDARDS:
