Coupon Collecting Problem: Find the Expectation of Boxes to Collect All Toys
Problem 750
A box of some snacks includes one of five toys. The chances of getting any of the toys are equally likely and independent of the previous results.
(a) Suppose that you buy the box until you complete all the five toys. Find the expected number of boxes that you need to buy.
(b) Find the variance and the standard deviation of the event in part (a).
Add to solve later 
