I watched Fermat’s Room — a mathematical thriller in Spanish language — few weeks ago. Although I did enjoy watching this movie, I am hesitant to recommend it due to sloppy direction (too pretentious, IMO) and average acting performances. But the premise on which the movie is based was quite intriguing: Four mathematicians are invited by an anonymous stranger (Fermat) to solve a great mathematical enigma. But soon after they convene, they get trapped in the room and must solve puzzles in order to survive. The room, with moving walls, begins to shrink as soon as they receive the puzzle from the host and it won’t stop contracting until they solve the puzzle.
Disappointingly, the puzzles were quite basic – most of them are classic riddles that I was already familiar with. I’ve listed some of them below:
- Using a 4 minute hourglass and a 7 minute hourglass how would you measure exactly 9 minutes?
- You have three opaque boxes. One box contains chocolate candies, another contains mint candies, and the last box contains a mixture of chocolate and mint. The boxes are labeled Chocolate, Mint and Mixed. None of the boxes are labeled correctly. You can take one candy out of each box (without looking directly into the box) and see what you get. What is the minimum number of boxes you have to open (and take one candy out) to assign correct labels to all boxes?
- There are three switches outside a room. One of them controls a lightbulb that’s inside the room, while the other two are not connected to anything. You can turn the switches ‘on’ or ‘off’ and also enter the room to see the lightbulb. What is the fewest number of times you will need to enter the room to determine which switch is connected to the bulb? (You can’t see if the lightbulb is ‘on’ or ‘off’ from the outside. And all switches are in the ‘off’ position when you start.)
- A mother is 21 years older than her son. In exactly 6 years, the son will be one-fifth his mother’s age. The question is: what is the father doing right now?
I think the following is probably the best one in the lot:
- A student asks his professor: “What are the ages of your three children?” The professor replies: “If you multiply their ages you get 36, and if you add them you get my house number.” “I know your house number, but that’s not enough information!” says the student. To that the professor answered: “True. The oldest lives upstairs.” What are the ages of the three children?
And finally, a classic Martin Gardner riddle: What is special about the number 8,549,176,320?
[Picture Courtesy: IFC Films]