Tonight the entire Yahoo! Web Messenger went out to dinner together (photos coming soon) and had a very enjoyable time. Following the dinner, on the way home Chris (head project manager) gave my friend Ben, Henri (my boss), and I two mind puzzles. One’s easier than the other, but both have had us all stumped for a bit. We decided to tackle the harder one first and after working as a team on it for about an hour at the office, we decided to head home to our respective homes and call it a night. Unfortunately, I can’t get the problems out of my head and have been pondering them since. The two mind puzzles are:
2 Burning Rope Problem
You are given two ropes which when lit take one hour to burn. Neither rope burns at the same rate and neither burn at a consistent rate. Your task is to light the burning ropes and use them to determine exactly when 45 minutes has passed.
Magician/Assistant 52 card trick
A magician has a standard deck of 52 cards (aka four suits of 13 cards each). The magician removes five cards from the deck and discards the rest. He then chooses one as his card, pockets it, and then leaves four cards on the table in a straight line without overlapping and all turned in the same fashion. The magician leaves the room and then the assistant comes in and is immediately able to say the exact card the magician had. How do they do it? There are no secret tricks, just basic mathematics.
I think I might have a solution now to the first one (not going to say it and ruin your challenge), but the second one still has me a bit stumped. Yes, one could cheat and look it up on the Internet, but what is the fun in that? Ponder these and see if you can come up with the answer!