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03-17-2002, 09:55 PM
|  | Usagi Yojimbo | | Join Date: Jul 2000 Location: The Birthplace of American Democracy
Posts: 16,716
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You have two fuses.
The first fuse will itself out in 1 hour.
The second takes 2 hours to burn out.
These fuses do not necessarily burn at a constant rate along their length. For instance, though the total time for the first fuse to burn is 1 hour, it might take 5 minutes for the first inch to burn then 10 minutes fo rhte second inch.*
Using these fuses you must measure a time period of exactly 45 minutes. Use as many matches as necessary. How can this be accomplished?
(* I know, I know. A real fuse is probably pretty constant in its burning if it is reliable at all in total time. For the purposes of the problem trust that the total times for the fuses are accurate and that these fuses exist.)
I'll give you a few days on this.
Since posting hidden is not available right now, here's what we'll do. Feel free to discuss the problem in the thread starting on Monday at noon EST. Anyone who doesn't want spoilers, don't read the rest of thread.
-JP |
03-18-2002, 08:41 AM
|  | Epinions Members | | Join Date: Jan 2002 Location: The Granite State
Posts: 10,466
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I am sitting on my hands - I have such a good answer to this (at least I like to think so)...
Can I post yet, huh, huh, can I? Can I post yet?  Leslie |
03-18-2002, 09:24 AM
|  | Premium Member | | Join Date: Nov 2000 Location: New York, NY, USA
Posts: 10,670
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My husband figured it out last night.  |
03-18-2002, 12:23 PM
| | Epinions Members | | Join Date: Jan 2002 Location: The Granite State
Posts: 10,466
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OK, it is ten after the hour, so here is my answer: Fold fuses in half. Light all the ends, including those made by the folding. They will burn for 45 minutes Leslie <- now waiting patiently to see if she figured correctly....
Last edited by phoenixx; 03-18-2002 at 01:13 PM.
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03-18-2002, 01:59 PM
| | Usagi Yojimbo | | Join Date: Jul 2000 Location: The Birthplace of American Democracy
Posts: 16,716
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Quote: Originally posted by phoenixx
OK, it is ten after the hour, so here is my answer:
Fold fuses in half. Light all the ends, including those made by the folding. They will burn for 45 minutes
Leslie <- now waiting patiently to see if she figured correctly.... | How do you know how long half a fuse (lengthwise) is going to burn?
-JP |
03-18-2002, 02:04 PM
| | Premium Member | | Join Date: Nov 2000 Location: New York, NY, USA
Posts: 10,670
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My husband figured this out last night. Absolutely, no question about it -- it's the right answer.
Shall I post it? |
03-18-2002, 02:48 PM
|  | Premium Member | | Join Date: Jul 2001 Location: New York
Posts: 1,313
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Husband here 
Here's the solution.
Light both ends of the one-hour fuse, and one end of the two-hour fuse. Since it is burning at both ends, the one-hour fuse will burn out in 30 minutes. At that time, the two-hour fuse will have 90 minutes of burn time remaining. Light its other end, and its burn time will be cut in half to 45 minutes. |
03-18-2002, 03:14 PM
| | Epinions Members | | Join Date: Jan 2002 Location: The Granite State
Posts: 10,466
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Quote: Originally posted by drmomentum
How do you know how long half a fuse (lengthwise) is going to burn?
-JP | You sound like my math teachers throughout my educational history.
I will have to do it on paper (yuck) to see if I can explain it and get back to you...
Leslie |
03-18-2002, 04:50 PM
| | Usagi Yojimbo | | Join Date: Jul 2000 Location: The Birthplace of American Democracy
Posts: 16,716
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Don't read hymie's answer if you don't want the solution.
Very nice job.
Leslie, I'm not completely clear on your solution because you seem to be lighting a lot of things at once and surely some of the things will burn out before others do.
Maybe I am just conFUSED.
-JP |
03-18-2002, 05:20 PM
| | Epinions Members | | Join Date: Jan 2002 Location: The Granite State
Posts: 10,466
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SIGH - honey came home, read my answer and laughed at me. I am sending stern looks his way. 
He says I should stick to Psychology, Enligh Literature, Writing, Music and "Computer Geek Stuff" and leave the math to professionals.
Honey will be dining out tonight.
(And I was all excited because I thought I'd understood a math-type puzzle)
: pout :
Leslie |
03-18-2002, 05:28 PM
|  | Hello, I'm Deb | | Join Date: Jun 2000 Location: Oregon
Posts: 7,222
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Quote: Originally posted by phoenixx
Honey will be dining out tonight.
(And I was all excited because I thought I'd understood a math-type puzzle) | LOL, Leslie, wanna come to my house for dinner? I teach math and I couldn't figure this out. My problem is figuring out why you'd use a match to light a fuse. Don't you just plug them in? 
Deb
having a Barbie moment
__________________ Support our Marines "If you want to be free, there is but one way; it is to guarantee an equally full measure of liberty to all your neighbors. There is no other." - Carl Shurz, German general and politician |
03-18-2002, 05:49 PM
|  | Premium Member | | Join Date: Jun 2000 Location: Lansing, MI, United States
Posts: 10,371
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Oh, Deb! I did the same thing!
__________________
Bridgette
"There are seven things that will destroy us: Wealth without work; pleasure without conscience; knowledge without character; religion without sacrifice; politics without principle; science without humanity; business without ethics." --Mahatma Gandhi
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03-18-2002, 06:31 PM
| | Premium Member | | Join Date: Nov 2000 Location: New York, NY, USA
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I, too, got stuck with not entirely understanding what one could do with a fuse other than light it and let it burn. 
When my husband came up with the crucial insight last night, ah, my foes! and oh, my friends! it gave a lovely light. |
03-18-2002, 07:11 PM
| | Usagi Yojimbo | | Join Date: Jul 2000 Location: The Birthplace of American Democracy
Posts: 16,716
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It probably didn't help that in my editing I removed the word "burn" from the description at one point. D'oh!
I should have added "fuses... as in for a bomb, or a stick of dynamite."
-JP (Who grew up with circuit breakers and has never had to deal with fuses for household electrical) (But I have used them in the car) |
03-22-2002, 01:43 AM
|  | Epinions Members | | Join Date: Jul 2000 Location: The Nutmeg State
Posts: 13,551
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Gah, so I wasn't the only one thinking of fuses like the things in your car that you replace when your stereo doesn't work, or fuses as in the things you go and check when you run the microwave and toaster oven at the same time, and then all the power in the kitchen stops working
Boy, am I glad!
And Leslie, your answer made perfect sense to me! |
03-22-2002, 01:46 AM
|  | Banned | | Join Date: Nov 2001 Location: Canada
Posts: 1,898
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Hey, no problem: a very nice puzzle. Never heard this one before. | |
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