Permutation or combination?

Question

You decide to invest 1000dollars in 1 out of 30 stock randomly every month for a year. After a year how many possible portfolios of stocks could you have?

Answer 1

It depends on  what you mean.

 

If you pick with replacement, i.e. from the same 30 stocks each month, then you get a huge number of possibilities, i.e.

(30)¹² 

 

If you pick all 12 stocks at one time, you can pick ₃₀C₁₂ = 30!/(12!*18!), which is also pretty big.