August 24, 2012

PRIME AND COMPOSITE NUMBER

PRIME NUMBER

Prime number is a number that has only 2 factors e.g 1 and the number itself.

How to check a given number is prime or not?

*Example 1, is 331 a prime number or not?

To answer it, we have to do three following steps

Step 1. Find the square root of 331 by calculator, the result is 18.193

Step 2. List all prime number which less than 18.193. These prime numbers are

2,3,5,7,11,13,and 17.

Step 3. Divide 331 with all prime numbers that already listed from step 2

If one of these prime number could divide 331 exactly without reminder, we can conclude 331 is not prime number and vice versa.


*Example 2 , is 221 a prime number or not?

To answer it, we have to do three following steps

Step 1. Find the square root of 221 by calculator, the result is 14.866

Step 2. List all prime number which less than 14.866. These prime numbers are

2,3,5,7,11,and 13.

Step 3. Divide 221 with all prime numbers that already listed from step 2

If one of these prime number could divide 221 exactly without reminder, we can conclude 221 is not prime number and vice versa.

*Example 3, is 527 a prime number or not?

To answer it, we have to do three following steps

Step 1. Find the square root of 527 by calculator, the result is 22.95

Step 2. List all prime number which less than 22.95. These prime numbers are

2,3,5,7,11,13,17,and 19.

Step 3. Divide 527 with all prime numbers that already listed from step 2

If one of these prime number could divide 527 exactly without reminder, we can conclude 527 is not prime number and vice versa.


Okay, Now your turn to answer this questions :


1. Is 527 a prime number or not?

2. Is 331 a composite number or not?

3. What is the composite number?

4. What is the prime number?

5. How to check a number is prime number or not?

6. Is 323 a composite number or not?

7. Is the prime number is always odd number?

8. List the odd number which is not prime number?


COMPOSITE NUMBER

The composite number is a number that has more than 2 factors.

*Example 1. Number 9 is a composite number, because has 3 factors e.g 1,3 and 9

*Example 2. Number 15 is a composite number, because has 4 factors e.g 1,3,5 and 15

*Example 3. Number 21 is a composite number, because has 4 factors e.g 1,3,7 and 21

*Example 4. Number 27 is a composite number, because has 3 factors e.g 1,3,9 and 27

*Example 5. Number 35 is a composite number, because has 3 factors e.g 1,5,7 and 35

BUT


*Example 6. Number 2 is a NOT composite number, because only has 2 factors e.g 1 and 2

*Example 7. Number 5 is a NOT composite number, because only has 2 factors e.g 1 and 5

*Example 8. Number 7 is a NOT composite number, because only has 2 factors e.g 1 and 7

So, number 2,5 and 7 are examples of prime number.

How about number 1? Is number 1 prime number or composite number?

The answer is number 1 has only one factor, so it's not included as prime NOR composite number.

lets learn maths :) :D

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