In: Advanced Math
Suppose when searching for a large prime, our first step is to sieve by eliminating the first n primes. How large should n be to speed up our search by a factor of 10? This requires careful thought and inventiveness before doing a computation.
How to approach this: Eliminating all odd numbers speeds up our program by a factor of 2, since we've eliminated half of the choices that are composite. If we also immediately disqualify multiples of 3, then we speed up our program by a factor of 3, since we have eliminated 2/3 of all composites. Check that that argument is correct. Now see what happens when you eliminate all of 2, 3 and 5. Again for 2,3,5,7. Now try to figure out the mathematical result and use it to solve for n.