how do you explain prime factors to a primary school child?

[workshy]

she gets it if it's obvious

eg 15=3x5

but if it's not made up of prime numbers she doesn't get it

any help?

[Itsjustafleshwound]

A prime number is just a number that is not divisible by anything other than 1 and itself isn't it???

[snowball3]

We make a factor tree, hard to show on here but
24 is made from say 2x12
2 is a prime factor, so that's the end of that branch
12 is made from say 2x6
2 is a prime factor so that's the end of that branch
6 is made from 2x3
both are prime so that's the end of all branches
so we have
2x2x2x3
which is
2 cubed x3
( It's much easier when you draw it!)

[YouChangeWithTheWeather]

There's two books on Amazon called Mrs J Rocks' and 'Mrs J Rules` - I can't remember which is literacy and which is numeracy, but they explain things very simply.

[snowball3]

PS it doesn't matter whether you start with 2x12 or 4x6 or 3x8, you will always end up with the same prime factors

[workshy]

thanks snowball3
I've seen the trees but she isn't usually very visual so didn't know if she would get them

I'll give it a go with her tomorrow :)