Re: Riddles (was: Lateral Thinking)

From: Dale Johnstone (
Date: Sat Jan 06 2001 - 11:11:49 MST

----- Original Message -----
From: "Eliezer S. Yudkowsky" <>
To: <>
Sent: Friday, January 05, 2001 10:47 PM
Subject: Re: Riddles (was: Lateral Thinking)

> Okay, here's a more precise version.
> 1) Take the key from A. Do this at 5:44PM.
> 2) Unlock B. Do this at 5:45PM.
> 3) Take the key from B. Do this at 5:46PM.
> 4) Unlock A. Do this at 5:43PM.
> Now, I want to say for the record that I actually *tried* this with two
> locked boxes each containing the other's key, and it *worked*. I didn't
> actually time it to the exact minute, and I had to reorder the steps
> slightly since I didn't have a time machine, but I *did* it and it
> *worked*, so I don't want to hear any further complaints.
> No, I did not put one of the boxes inside the other one. No, I was not
> standing inside either of the boxes. No, one of the boxes was not shaped
> like a key to the other. And no, the boxes were not made of wood. But I
> did check them, they were securely locked, and there was no way to get the
> key out of either one without unlocking it. And this was in *real life*,
> plain ol' physical reality, so you can be sure there were no meta-tricks
> there.

Possible solutions:

1) You have a third key.

2) You can unlock a box without the key.

3) Both boxes begin locked. Key A is inside the lock of Box B. Key B is in
inside Box A.
You unlock Box A (Step 4).
You put Key B inside Box A.
You take Key B from Box A (Step 1).
You unlock Box B (Step 2).
You put Key A inside Box B.
You take Key A from Box B (Step 3).

Hmm, no. I'm afraid this wouldn't satisfy me as a valid answer. Key A
starting inside the lock of B doesn't really count as being inside Box B.
Neither does placing each key inside the other boxes at different times.

4) The locks were combination locks & the keys were their numbers written on
pieces of paper.

5) The boxes were identical and so were the keys. You managed to unlock each
box with the key of the other by getting it to fall into the lock. Then
using something to turn the key from the other side (the outside) of the
lock. Tricky but possible.

Hmm, so what are these boxes made of anyway?

Dale Johnstone.

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