A special but common type of scenario is one in which a company has a promotion that is designed to make the customer purchase more of their product than they otherwise might. Although this can be aimed specifically at children, it really applies to all persons. The basic premise is that the company issues a "set" of different items or coupons and places one of the coupons in boxes of their product. The consumer does not know which of the coupons in the set they will get until they purchase the product and open the packaging. This situation is sometimes known as the "coupon collector's problem" or "cereal box problem" (since the coupons are often a set of toys found in a packet of cereal). This article analyses this problem generally and then demonstrates it, by using specific examples. It provides an interesting instance of how mathematics can be used to analyse an everyday problem while illustrating the important concept of modeling. Specific instances of its application include coin collecting by Lu and Skiena (2000). (Contains 4 tables.)