WOLFRAM|DEMONSTRATIONS PROJECT

Coupon Collector Problem

​
number of distinct coupons
50
seed random
1
If a package has one of 50 random baseball cards, how many packages do you need to buy to get a complete set? The expected answer is
50
H
50
≈225
packages, where
H
50
is the harmonic number
1/1+1/2+1/3+…+1/50
. Switching from baseball cards to coupons gives the coupon collector problem: if there are
n
different kinds of coupons and many of them are distributed randomly, the expected number of purchases necessary for a complete set is
n
H
n
.