Inside the drawer of a dressing-table in a dark room, there are 28 black socks and 28 brown socks. What is the minimum number of socks that I must take out of the drawer to guarantee that I have a matching pair?
Click here for the solution
Three. If I pick three socks, then either they are all of the same colors [in which case I certainly have a pair of the same color] or else two are of one color and the third is of the other color, so in that case, I would again have a matching pair.
Take from the pack the thirteen cards forming the suit of diamonds and arrange them in this order face downwards with the 3 at the top and 5 at the bottom: 3, 8, 7, Ace, Queen, 6, 4, 2, Jack, King, 10, 9, 5. Now play them out in a row on the table in this way. As you...