1. ## Counting problem

Janice is choosing some CDs from her collection to take to a party. She owns 10 jazz CDs, 15 pop CDs and 8 hip hop CDs.
Fred is bringing 6 pop CDs to the party. Janice knows that Fred owns 4 of the pop CDs that are in her collection. How many pop CDs must she bring to the party to ensure that between them they have brought at least 9distinct pop CDs?

I thought about the pigeonhole principle,but it turn out the answer is 20766240. Can someone pls help

2. ## Re: Counting problem

Worst case scenario is that Fred brings all 4 pop CDs that Janice owns. If Janice brings 11 of her pop CDs, and worst case she picks all 4 as well, then there will be a total of 8 CDs that are duplicate, and 9 that will be distinct (2 from Fred and 7 from Janice). No idea where your final answer came from.

3. ## Re: Counting problem

Originally Posted by majamin
Worst case scenario is that Fred brings all 4 pop CDs that Janice owns. If Janice brings 11 of her pop CDs, and worst case she picks all 4 as well, then there will be a total of 8 CDs that are duplicate, and 9 that will be distinct (2 from Fred and 7 from Janice). No idea where your final answer came from.
That is exactly how I worked out. I'm currently waiting an email from my teacher. If the answer is actually as she claims it to be, then I shall let you know ASAP
Thanks anyway