How do you learn prime number from 1 to 100?

Answer 1

Write out the numbers 1 to 100 in 10 rows. Cross out 1. Start at 2 and cross out multiples of 2. That would eliminate all the rest of the even numbers. Go to the next uncrossed-out number (3) and cross out all of its multiples. Some of them will already be crossed out. You can stop by the time you get to ten. All of the uncrossed-out numbers are prime.