Approximation probability math

Question

Every mushroom is edible with the probability of 0.95, independent of other picked mushrooms.

How many mushrooms would have had to be picked so that the probability that at least 300 would be edible would be at least 0.99?

Answer 1

P(n,x,p) = [n!/x!/(n-x)!]*p^x*(1-p)^n-x

Where p=0.95, x=300, and n is the number of trials needed to achieve P≥0.99, n must be at least 326.