Put back sampling and do not put back sampling

Consider n balls, n white, remaining black, calculate the probability of the k to take out the white ball when the sample is put back and not put back, respectively.

Put back: p=n/n

Not put back: The first time must be n/n

Second time: Considering the first possible removal of white or black, p=p (Np-1)/(N-1) + (1-p) np/(N-1) =n/n

......

K Times: p=n/n

Or consider this: by symmetry, the probability of each spin placed struck being taken out in any one fetch is the same (? ）。

Put back sampling and do not put back sampling