Here's a cool thing...
08042010, 01:59 PM


Write out the numbers 120 on a sheet of paper. Write them balloon style so students can color them in when given the direction to do so. Since 1 is not prime or composite, it doesn't get colored in at all.
Two is prime so the whole number two gets colored in (red).
Three is prime, but different than two, so gets colored in a different color (green).
Four is composite. Draw a line dividing the number in half horizontally. Since its factors are two and two, draw the upper half red as well as the lower half.
Five is prime, but different than two and three, so gets colored in a different color (blue).
Six is composite. Draw a line dividing the number in half horizontally. Since its factors are two and three, the upper half is colored red and the lower half is colored green.
Seven is prime and needs to be a different color than what has been used so far (yellow).
Eight is composite. Draw a line dividing the number in half horizontally. The upper half will represent the 2 in 2 x 4 and will be colored red. The lower half represents 4, so draw a line dividing the lower half in half again and color both sides red as well. In this manner, you are also teaching prime factorization (2 x 2 x 2 =8)
Keep going in this manner, filling in the sheet. At the end, students can visually see the prime numbers (solid colors) versus the composite numbers (multicolored or divided into smaller parts).
If this is not clear to you, let me know. I have an example at school and could post a copy.
