Name: Connie
Who is asking: Parent
Level: Elementary
Question:
My son can't remember what a composite number is, what a prime number
is and the explaination of factors and common factors. Help!
Hi Connie,
A prime number is an integer, larger than 1, that has no divisors except itself and 1. For example 2, 3, 5, and 7 are primes. 4 is not a prime since 2 divides 4, likewise 6 and 12 are not primes because 3 divides both of them.
A composite number is an integer, larger than 1, that has more than two divisors. Thus 6 is composite since 1, 2, 3 and 6 are divisors of 6.
A factor of an integer is an integer that divides it. Thus 2 is a factor of 12 since 2 divides 12. Likewise 4 is a factor of 12.
If you have two integers then a common factor is an integer that divides each of them. Hence 3 is a common factor of 6 and 12 since 3 divides both 6 and 12. Likewise 5 is a common factor of 10 and 25.
I hope this helps,Penny