The hint - world cup medallions
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Let Xn= Tn - Tn-1 where Tn is the number of medallions collected when you first own n different medallions. Hence X1=1, but what do we know about Xn for other values of n?
It might also help to remember, if X and Y are random variables, the average (or expectation) of X + Y is the same as the expectation of X + the expectation of Y. In symbols we may write this as
Have fun!
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