Algebra Den

Sieve of Eratosthenes

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:-

1	2	3	4	5	6	7	8	9	10
11	12	13	14	15	16	17	18	19	20
21	22	23	24	25	26	27	28	29	30
31	32	33	34	35	36	37	38	39	40
41	42	43	44	45	46	47	48	49	50
51	52	53	54	55	56	57	58	59	60
61	62	63	64	65	66	67	68	69	70
71	72	73	74	75	76	77	78	79	80
81	82	83	84	85	86	87	88	89	90
91	92	93	94	95	96	97	98	99	100

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.