Now I understand it.
I just learnt this principle. I am doing a problem in which there's a box with many red socks, green socks and blue socks. First question was how many minimum socks should I pick out without looking to be absolutely sure to get a matching pair. This was an intuitive one. However, I am having trouble understanding an extension of this problem: how many socks should I pull out without looking to be absolutely sure that I have a three pairs of a color.
The book said 3 pairs. I presume it is 3 pairs of one color.
When I thought about it, I cannot understand why there should be a solution at all. How can I be absolutely certain, when I can pick out a red sock, a red sock, a red sock, infinite number of times. If I dont understand this, then I cannot proceed with learning this principle, as I do not see how it applies or relates.