How do you figure out what are the prime numbers between 1-50?

Answer 1

Write out the numbers 1 to 50 in 5 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 eight. All of the uncrossed-out numbers are prime.