Let's find all the prime numbers.
1,3,5,7,9,11,13,15,17,19
They are not divisible by 2.
Put that into a fraction, where the amount of numbers is the numerator and the total amount of numbers is the denominator.
10/20
That is half of 20.
So, 50% of the 20 first natural numbers are prime.
I hope this helps!
~cupcake
