110. 3 There are 2005 different real numbers written on the back of 2005 cards. Each time a question is asked, you can point to any three cards and ask about the set of three numbers written on them. How many times at least must you ask to definitely find out what numbers are written on the back of each card?

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Solve 1003 questions.
Assume that $N$ questions have been asked. Clearly, each card must participate in at least one question; otherwise, it would be impossible to determine the number on that card. Suppose there are $k$ cards that each participate in exactly one question. Then, in the same question, it is impossible to encounter two such cards. In fact, if two such cards participate in the same question, then if the numbers written on these two cards are swapped, the answer we receive would not change at all, making it impossible to determine which number is written on each card. Therefore, $k \leqslant N$. The remaining cards each participate in at least two questions. If we sum the number of questions each card participates in, then we have $3 N \geqslant k + 2(2005 - k) = 4010 - k \geqslant 4010 - N$, which means $2 N \geqslant 2005, N \geqslant 1003$.
Next, we will show how to achieve the goal with 1003 questions. Remove one card and divide the remaining cards into 334 groups, each containing 6 cards. Number the cards in each group from 1 to 6, and ask three questions for each group: $(1,2,3)$, $(3,4,5)$, and $(5,6,1)$. In this way, in each group, the cards numbered $1,3,5$ each appear in two questions, so they can be uniquely determined; while the numbers written on the cards numbered $2,4,6$ each appear in one question. Thus, through $\frac{2004}{6} \times 3 = 1002$ questions, we can determine the numbers on 2004 cards. The remaining one question is used to determine the number on the card that was set aside (just ask it together with any other two cards once).