Finding the Prime Numbers

For finding the prime numbers we write all the whole numbers from 1 to 100 in a 10-square table and then follow the following steps.

Step 1: 1 is a unique number, so we do not consider it.

Step 2: We cross out all the multiples of 2 except 2.

Step 3: We cross out all the multiples of 3 except 3.

Step 4: We cross out all the multiples of 5 except 5.

Step 5: We cross out all the multiples of 7 except 7.

Step 6: Now, we encircle all the remaining numbers except 1.

Finding the Prime Numbers

All the numbers encircle are prime numbers. Those which are crossed out are the composite numbers. 1 is a unique number.

We see that 25 numbers are prime numbers out of the first 100 numbers.

They are: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97

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