# Kareem has 216 role-playing game cards. His goal is to collect all 15 sets of cards. There are 72 cards in a set. How many more cards does Kareem need to reach his goal?

Factors and multiples
Since there are 72 cards in a set, then Kareem needs to collect a total of $$\displaystyle{15}×{72}={1080}$$ cards. Since Kareem currently has 216 role-playing game cards, subtract 1080 by 216 to find how many more he needs:
$$\displaystyle{1080}−{216}={864}$$