Let’s learn how to find prime numbers from 1 to 100
We follow the steps

Cross out 1 as it is neither prime, nor composite

2 is prime as its factors are 1 & 2.
So, all its multiples will have 2 as factor. So, cross all those numbers.
Numbers like 4, 6, 8, 10, 12, 14, … will be crossed out

3 is prime as its factors are 1 & 3
So, all its multiples will have 3 as factor. So, cross all those numbers.
Numbers like 6, 9, 12, 15, 18, 21, 24, .... will be crossed out
 Repeat the process for other numbers until we find all the prime numbers
Thus, Prime numbers from 1 to 100 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