# Expected value of random variable which is the number of drawns required

An urn has n balls and we take balls from it with replacement until each ball has been drawn at least one. X denotes the number of draws required. What is the expected value and variance of X? I think X is at least n, is it true? And how should I find the expected value of it?

• This is known as the coupon collector problem, – lulu Nov 12 '18 at 15:29
• Thank you so much – werlless Nov 12 '18 at 15:36