A Puzzling Lunch

We had a nice lunch today with Rona’s dad, as we do every week, and today’s theme of conversation was puzzlers. The first two puzzlers I posted many years ago on Rubicon Games’ site. Both of those were donated by Dr. Bob Coury. I don’t think he came up with the puzzles, but he and his fellow applied-math-doctorate friends at RPI had fun answering them and passed them along for my use on the site. The other puzzler was Robert’s contribution to a puzzlingly fun afternoon.

I’ll post them here, but I’m not going to post the answers yet. I wouldn’t want to spoil your (my) fun, after all. Are you ready? Stretch those synapses and give these a try…

Puzzler #1: Body Talk

Name ten parts of the human body that have only three letters in their name.

THE RULES: You can’t look anything up. There are ten words on the official list, and only these words count. These body parts can be found on both male and female humans–there is nothing gender-specific. None of the answers is part of a compound word. Slang terms don’t count–these are all real, simple words from the dictionary, that you’ve known since kindergarten.

It’s harder than it sounds–good luck!

Puzzler #2: Midnight Escape!

Four brothers, Al, Bert, Carl, and Dan, just escaped from prison. Three of them were injured during the escape. They have managed to bring one flashlight with them. Good thing, because it’s night, and it’s dark.

They’re running through the woods when they come to a rickety old rope bridge over a gorge. The cops are seventeen minutes behind them–if the four of them find a way to make it over the bridge in seventeen minutes (or quicker), they can break the rope bridge and disappear into the night. If one goes back to jail, he’ll make sure the others do, too. If any of them dies, the others won’t have the will to go on.

With the flashlight, the uninjured guy (Al) can make it across the bridge in 1 minute. The others (Bert, Carl, and Dan), due to their wounds, can make it across in 2, 5, and 10 minutes, respectively.

In what order should they cross the rope bridge that will take them no more than 17 minutes?

The rules:

1. A maximum of two people may cross the bridge at the same time. Put three on and it’ll break and they’ll be rock food.
2. No one can be on the bridge without holding or being able to touch the flashlight. In the dark they’d fall off, and become rock food.
3. The flashlight must always be in one of the four brothers’ possession.
4. If they try to throw the flashlight, it’ll fall into the gorge–and it and anyone on the bridge will become rock food. The flashlight can only be transferred between people who are standing next to each other, directly from hand to hand.
5. If two people are crossing the bridge they move at the speed of the slower individual. Otherwise the hurt person screams in pain, falls off the bridge (taking the other with him) they both become rock food (as does the flashlight), and the remaining two go back to prison.
6. No killing off Dan (the 10 minute guy).
7. No juggling of prisoners so that two are in the air while two are on the bridge.
8. No piggy-back rides.
9. No laying an ambush for the cops to buy you more time.

There is no catch to this! Just figure out what order will get them across the bridge in seventeen minutes, and they’re home free. Screw it up, and they’re likely to drag you back to prison with them!

Puzzler #3: Counterfeit Coin Conundrum

You have ten rolls of coins, with 40 coins in each. One of the ten rolls consists of 40 counterfeit coins, but you don’t know which one it is. You have a digital scale that can measure weights up to 50 pounds. The counterfeit coins are indistinguishable from the legal coins in every way except that they weigh slightly less–.90 ounce for 1 fake coin instead of 1 ounce for 1 real coin.

How can you tell precisely which roll of coins is counterfeit in one weighing on your scale?

NOTE: "One weighing" means one act of placing things on the scale and reading the number. If you then remove something from the scale and read the number again that is another weighing, and doesn’t count.

If you have questions about any of the puzzlers or if you want to try out an answer, leave a comment!