Probability - no idea where to start

tuthu said:
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It's a little hard to interpret, isn't it?

I'm not entirely sure, but as I read it, the numerators tell you how many cards there are in each packet that he hasn't seen in previous packets in the list; that implies that he had no cards before, and that the first packet must have had a duplicate card. From this, we could work out how many distinct cards there are in all (which I think will be needed for some subsequent question). It could be helpful to see the entire problem, which could give clues as to its meaning.

But I think (a) is very simple. How many new cards are there that could be in the next packet? What fraction of the packet would that be?
 
thanks for responding - really appreciated. The answer for this is 60%, which suggests that the number of cards needed is 3, and so the fraction is 3/5. But I can't think why this can't be 4 or 5 brand new distinct cards over 5 cards (i.e. 5/5 = 100%).

Part (b) of the question just asked to convert the fractions into percentages (i.e. 4/5 = 80%)
 
tuthu said:
thanks for responding - really appreciated. The answer for this is 60%, which suggests that the number of cards needed is 3, and so the fraction is 3/5. But I can't think why this can't be 4 or 5 brand new distinct cards over 5 cards (i.e. 5/5 = 100%).

Part (b) of the question just asked to convert the fractions into percentages (i.e. 4/5 = 80%)
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The problem is as simple (mathematically) as it looked to me, which seemed too trivial!

You are told that he needs only "three more different cards to complete his set". That means that there are only 3 cards he doesn't have yet, and the greatest possible number of new (not yet seen) cards is 3! And 3 new cards out of 5 is 3/5.

This is not really a math problem, but one of reading comprehension in a poorly written problem.
 
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