To calculate the probability of some event with probability P coming true at least once out of N total tries, you do 1 - ((1 - P) ^ N), not P * N as you've done

To calculate the probability of some event with probability P coming true at least once out of N total tries, you do 1 - ((1 - P) ^ N), not P * N as you've done. Doing this, your final figures should be 12.1% and 96.8%. For the expected number of times it would happen though, you are right, it would be three or four times per year on average for the second case.