> This is tantamount to saying that the probability that A is prime

increases as A increases. QED.

Alan pointed out the Prime Number Theorem, which is truly important, but

also consider common sense: past 2, half of the numbers composites

divisible by 2. Past 3, half of those remaining numbers are divisible

3, past 5, 1/5 are divisible by 5... obviously the density is going down

(on the average).

Good luck!> Let A be a natural number. Let S be the set of all prime numbers such

So far okay...

> that any element of S is less than the step function of the square root

> of A.

> Define the probability that A is a prime number as the quotient (A-S)/A.

... but why exactly would this ratio describe the probability of a number

being a prime?

Peter