Thread: Need help with this problem....

9. Eight varieties (including cherry centre) of chocolates are available and Don wants to buy 30 chocolates.

(a) How many choices does he have?

(b) How many choices does he have if his friend, Angela, insists that at least one chocolate should have a
cherry centre?

Originally Posted by aamiri

9. Eight varieties (including cherry centre) of chocolates are available and Don wants to buy 30 chocolates.

(a) How many choices does he have?

(b) How many choices does he have if his friend, Angela, insists that at least one chocolate should have a
cherry centre?

(a) This is the same as putting 30 unlabeled balls into 8 labeled bins where a bin is allowed to receive 0 balls. There is info here

http://www.johndcook.com/TwelvefoldWay.pdf (pdf)

and here

Stars and bars (probability) - Wikipedia, the free encyclopedia

(b) Take answer from (a) and subtract number of ways to place 30 unlabeled balls into 7 labeled bins.