Arrays, Dimensions, Factors, Prime, Composite, Square

This picture shows and array of 23 and the right side is an array of 29.  Introduced the term prime.  Have you heard this word before?  Where?  (A student had a great point saying she primed her house.  Yes, our English language is great two different meanings for the same word)

The students decided that these were prime numbers because they were odd numbers so we had to show them an example of a different array that is also an odd number.

This array of 45 is odd but the students said is was not prime.  When asked why they said it has more than one array and prime numbers can only have one array.  (Getting closer)
Then we tallked about factors and how prime numbers have only two factors (1 and itself). 
So what is a number like 45 called if it is not prime?
Introduced the word Composite.  How should we define composite numbers?  (Any number that has more than two factors)  Yes, a student used those exact words to describe composite without looking the word up in a dictionary.

So many good examples.  Our last term is a square number.  Where do you see an example of a square number?  An array of 81 has a square on it.  What are the dimensions of the square number?  9 by 9.
So how should we define a square number?  A number that has two dimensions that are the same.

Not bad for the first week of school if I do say so myself.  These kids were on target and I had a blast teaching today.