Post Cereals has decided to run a promotion whereby they are putting 10 differen
ID: 3021493 • Letter: P
Question
Post Cereals has decided to run a promotion whereby they are putting 10 different Yu-Gi-Oh cards in specially marked boxes of cereal. Card number 3 is the most sought after card in the series.
a. What is the probability that you will get card number 3 without having to buy more than 3 boxes of specially marked cereal? (Assume that all cards are equally likely).
b. Suppose you are unlucky and you don’t get card number 3 in the first 3 boxes you buy. On average, how long will you have to wait to get card number 3?
Explanation / Answer
A)Because you have 10 different yugioh cards, and all would be equally likely, the chance of getting card 3 is 1/10 or 10%. Since you buy three boxes, the chance is 1/10+1/10+1/10 or 3/10 or 30%.
B) The average time it would take for something to happen is the same as the theoretical probability of 100%. This means the average time it would take is 10 boxes, because 100% = 10/10.