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## Sieve of Eratosthenes

The Steps to be followed are as:-

**Step 1 = ** Strike Out 1 because 1 is neither a Prime Number nor a Composite Number.

**Step 2 = ** Write 2 in bold.

**Step 3 = ** Strike Out all the Multiple of 2 other than itself. e.g. 2, 4, 6, 8, 10, 12 ........and so on till 100.

**Step 4 = ** After Step 3, the next non-strike number you will find is 3. Write 3 in bold.

**Step 5 = ** Strike Out all the Multiple of 3 other than itself. e.g. 9, 15, 21, 27, ........and so on till 100.

**Step 6 = ** After Step 5, the next non-strike number you will find is 5. Write 5 in bold.

**Step 7 = ** Strike Out all the Multiple of 5 other than itself. e.g. 25, 35, 55, ........and so on till 100.

**Step 8 = ** After Step 7, the next non-strike number you will find is 7. Write 7 in bold.

**Step 9 = ** Strike Out all the Multiple of 7 other than itself.

**Step 10 = ** Continue this process, untill all the numbers in the table are either Strike out or written in Bold.

**Step 11 = ** All the Strike Out Numbers are **Composite Numbers** (except 1).

**Step 12 = ** All those numbers which are written in Bold are **Prime Numbers**.

__Explanation__

In Third Century B.C. a Greek Mathmatician **" Eratosthenes "** developed a table to List all the Prime Numbers and Composite Numbers between 1 to 100. This method is known as **" Sieve of Eratosthenes"**

The Table developed by him is as:-

2 | 3 | 5 | 7 | ||||||

11 | 13 | 17 | 19 | ||||||

23 | 29 | ||||||||

31 | 37 | 39 | |||||||

41 | 43 | 47 | |||||||

53 | 59 | ||||||||

61 | 67 | ||||||||

71 | 73 | 79 | |||||||

83 | 89 | ||||||||

97 |

The Steps to be followed are as:-