1. Prime and Composite Numbers

2. Introduction Me: I am in compacted math and I will show you the math concept of prime and composite numbers. Concept: Every number in the number line is either a prime or composite number.

3. Prime Numbers Definition of a prime number :  A number that can only be divided by the number one and itself. Examples: 2, 3, 71,  2/1=2  3/1=3  71/1=71  The only prime number that is even is 2 because every other even number can be divided by 2.

4. Composite Numbers Definition of a composite number:  A number that can be divided by not only itself and one but also by at least one other number. Examples: 4, 8, 24  4/1=4; 4/2=2  8/1=8; 8/4=2; 8/2=4  24/1=24; 24/4=6; 24/6=4; 24/12=2; 24/2=12; 24/3=8 24/8=3  Not all odd numbers are prime

5. How do you know?  How would you know if the number is prime or composite? Answer: Divisibility Rules 1. all numbers 2. even 3. Add all digits in the number together and see if the sum is divisible by 3. 4. If the last 2 digits are divisibly by 4 or if the number ends in a double zero 5. The number has to end in a zero or five 6. If the number is divisible by 2 and 3 7. Take the last digit of the number double it and subtract it from the number in front of it, if the difference is divisible by 7 the number is too 8. Last three digits are divisible by 8 9. If the sum of the digits are divisible by 9

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