A trading card series has 200 different cards in it, which are sold in 5-card packages.

Each package has a random sampling of the cards (assume that any card of the 200 has an equal chance of being in a package).

On the average, how many packages will need to be bought to collect the complete series if...

A: all the cards in a package will always be different

B: a package can have repeats

Ok, heres my idea im not sure of it though but anyway..

your chance of getting a new card for every card in the first pack is 1, you can't have any doubles.

For the 2nd pack chance of getting a new card:
1st card: 195/200
2nd card: 194/199
3rd card: 193/198
4th card: 192/197
5th card: 191/196

Now for the 3rd pack
1st card: 190/200
2nd card: 189/199
3rd card: 187/198
4th card: 186/197
5th card: 185/196

And so on until you reach the end

I think this idea might be the right solution but i have no idea of how to do the maths needed to figure it out, i think levik is some sorta maths fan, im pretty sure it'd involve series but thats as much as i can figure out of it.

Posted by Eamon on 2002-05-10 00:01:49