Prime Numbers & Composite Numbers

Hi, I'm Rebecca. And in this film we're going to look at some strategies for teaching prime numbers and composite numbers. So let's begin by revising those two terms. All whole numbers have at least two factors. They have one and they have themselves in their times tables. And numbers that only have one and themselves in the times tables are called prime numbers. For example, the number 13 only has the factor 1 and 13 in its times table, so it is a prime number. Composite numbers are numbers that are made up of more than two factors. So, for example, the number 14 has the factors 1, 2, 7 and 14 in its times tables. So they are composite numbers. One good way of investigating composite numbers and prime numbers is, is to use base 10 blocks. So let's have a look at what this looks like here. I have some base 10 blocks and the question is 11 a prime number or a composite number? So let's investigate. Now we can move our base 10 blocks and we can see that we could make 11 groups of one. We could make one big group of 11. Can we split them into twos? We can't split them into equal groups of two because we have a remainder. What about threes? We can't split them into threes because they have a remainder. So here from doing this, we can see that the only factors of 11 are are 1 and 11. So it is a prime number. We can also use arrays to investigate composite and prime numbers. So, for example, here we have how many arrays can we make to show the number 12? Well, here we have one group of 12. This array represents six groups of two or two groups of six. And this array here represents four groups of three. So four times three. So from this we can see that the factors of 12 are 1, 12, 6, 2, 3 and 4. So 12 is a composite number. You can also investigate prime numbers and composite numbers using a hundred square to look for patterns. So there you go. There's just some simple ideas for teaching prime and composite numbers.