M-Magic 01 || Finding Prime Number Less Than 100

Finding Prime Number Less Than 100

Greek Mathematician Eratosthenes, in the third century B.C. Let us see the method. List all numbers from 1 to 100, as shown below.

Eratosthenes Sieve

Step 1 : Cross out 1 because it is not a prime number.

Step 2 : Encircle 2, cross out all the multiples of 2, other than 2 itself, i.e. 4, 6, 8 and so on.

Step 3 : You will find that the next uncrossed number is 3. Encircle 3 and cross out all the multiples of 3, other than 3 itself.

Step 4 : The next uncrossed number is 5. Encircle 5 and cross out all the multiples of 5 other than 5 itself.

Step 5 : Continue this process till all the numbers in the list are either encircled orcrossed out.

All the encircled numbers are prime

numbers. All the crossed out numbers, other than 1 are composite numbers.

This method is called the Sieve of

Eratosthenes.