Author Topic: Logic Puzzles  (Read 10042 times)

joshdick

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« on: April 11, 2005, 04:24:09 PM »
There are two lengths of rope.
Each one can burn in exactly one hour.
They are not necessarily of the same length or width as each other.
They also are not of uniform width (may be wider in middle than on the end), thus burning half of the rope is not necessarily 1/2 hour.

By burning the ropes, how do you measure exactly 45 minutes worth of time?



Give a barrel with an indeterminate amount of water in it, how can you discern whether it is exactly half-full without measuring it conventionally?
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ober

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« Reply #1 on: April 11, 2005, 04:29:01 PM »
1) Use a watch?
2) Cool it down and then bring it back to warm temp... look for a condensation line.

joshdick

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« Reply #2 on: April 11, 2005, 04:34:40 PM »
1) You forgot your watch that day. That's why you're burninating ropes to measure time.

2) There's an easier way than that.
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pianorain

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« Reply #3 on: April 11, 2005, 04:37:07 PM »
Quote from: joshdick
There are two lengths of rope.
Each one can burn in exactly one hour.
They are not necessarily of the same length or width as each other.
They also are not of uniform width (may be wider in middle than on the end), thus burning half of the rope is not necessarily 1/2 hour.

By burning the ropes, how do you measure exactly 45 minutes worth of time??
Seems to me that you could cut one rope down the entire length of the rope, resulting in two half-ropes that would burn in 30 minutes.  Cut one of those halves in half (once again, down the entire length), and you'd have a half-rope that would burn in 30 minutes and two quarter-ropes that would burn in 15 minutes.  Start the half-rope, and start a quarter rope when the half-rope is finished.
[post=3832]axon[/post]: I hate it when people copy my originality :p

Perspective

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« Reply #4 on: April 11, 2005, 04:39:32 PM »
1. Start burning one rope and count the exact number of bars of "Stairway to Heaven" that you can hum in the time the rope takes to burn. (repeating the song as necessary).  Now re-hum 3/4 of the total amount you hummed in the first place and you have exactly 45 mins (be sure to keep your tempo even!). hah, i didnt even need the second rope.

2. Didnt whats his face do that in lethal weapon?

ober

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« Reply #5 on: April 11, 2005, 04:42:09 PM »
Quote from: pianorain
Seems to me that you could cut one rope down the entire length of the rope, resulting in two half-ropes that would burn in 30 minutes.  Cut one of those halves in half (once again, down the entire length), and you'd have a half-rope that would burn in 30 minutes and two quarter-ropes that would burn in 15 minutes.  Start the half-rope, and start a quarter rope when the half-rope is finished.

Except for the fact that he said 1/2 the rope does not mean 1/2 the time.

Perspective

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« Reply #6 on: April 11, 2005, 04:42:30 PM »
pianorain: wouldnt the rope fall apart if you cut it length wise? I think my solution is much more feasable.

joshdick

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« Reply #7 on: April 11, 2005, 04:43:35 PM »
Ober's right about that.

Perspective, but what if I can't remember all the words? ;)
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Govtcheez

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« Reply #8 on: April 11, 2005, 04:47:26 PM »
> Perspective, but what if I can't remember all the words?

Then you're a horrible horrible person.

There are lots of ways to do the second one.  I prefer pouring the contents into a barrel with exactly half the volume of the first.

pianorain

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« Reply #9 on: April 11, 2005, 04:48:01 PM »
Quote from: joshdick
Ober's right about that.
Hmm...not the way I read the rules.
Quote from: joshdick
They also are not of uniform width (may be wider in middle than on the end), thus burning half of the rope is not necessarily 1/2 hour.
By cutting the rope length-wise instead of the usual manner, I'm taking care the "not uniform width" problem.  Both halves would be the same.
Quote from: Perspective
pianorain: wouldnt the rope fall apart if you cut it length wise? I think my solution is much more feasable.
Bah...that's an exercise left for the reader. ;)
[post=3832]axon[/post]: I hate it when people copy my originality :p

joshdick

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« Reply #10 on: April 11, 2005, 04:48:30 PM »
But alas, Govtcheez, you have but that one barrel.
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ober

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« Reply #11 on: April 11, 2005, 04:50:56 PM »
new try:
1)

shit... I cheated and looked it up on the net.  Nevermind.

2) I didn't look this one up, but if you measured the height of the barrel and the height of the water inside, you could tell.

pianorain

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« Reply #12 on: April 11, 2005, 04:52:32 PM »
Quote from: joshdick
Given a barrel with an indeterminate amount of water in it, how can you discern whether it is exactly half-full without measuring it conventionally?
Cut a hole in the barrel at the half-way point.  If water leaks, then it's more than half-full (for a while, anyway).  Then choose a solution:

#1) Place a rock in the barrel (preferably small).  If water leaks out, then the barrel was half-full or you used too large of a rock.  If water does not leak out, then the barrel was not half-full.

#2) Add water until water begins to leak out.  Wait until the water has stopped.  Now the barrel is half-full.
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Govtcheez

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« Reply #13 on: April 11, 2005, 04:59:50 PM »
Quote from: joshdick
But alas, Govtcheez, you have but that one barrel.

Hey, fuck you, you don't know what I have.  You think just cause I'm poor I don't have a barrel?

PS This "brainteasers" are always fucking dumb because there're a million possible answers, but only one is the "correct one", and the only way you know that is if you heard it before.  The best ones like this are the dead fisherman and the man that hangs himself.

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« Reply #14 on: April 11, 2005, 05:14:26 PM »
Tilt the barrel until you see the bottom. If you are wet, the barrel was more than half-full. If you are dry and the water reaches the top edge of the barrel it was exactly half-full.