4 boxes, equal probability, containing any one of 7 collector cards. what probability of 4 identical cards?

Question

Suppose you buy 4 boxes of cereal and each box has an equal probability on containing any one of the 7 collector cards. What is the probability of getting 4 identical cards?

Answer 1

The first box defines the card the other three boxes have to match. The odds any one of the other three boxes have the same card is 1 in 7. So, the odds for all 4 boxes having the same card is 1/7^3 = 1 in 343.