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# Boil this egg for exactly 3 minutes

6 replies to this topic

### #1 bonanova

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Posted 14 October 2007 - 08:34 AM

You want to boil a perfect 3-minute egg.

For a timer, you have only two 4-minute fuses, that do not burn at an even rate.

Can you have breakfast without a runny [or overly hard] egg?
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The greatest challenge to any thinker is stating the problem in a way that will allow a solution.
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### #2 Writersblock

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Posted 14 October 2007 - 09:30 AM

I think that

Spoiler for solution

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### #3 aforsy

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Posted 14 October 2007 - 08:08 PM

Here's my cheating solution: In my experience, a 3-minute egg will still be runny.
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### #4 slmo

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Posted 20 October 2007 - 12:36 AM

I think you light one fuse (Fuse A) on both ends and Fuse B on one end simultaneously. Once Fuse A has completely burned to the middle, 2 minutes have passed. Fuse B should have also burned for 2 minutes, so it will have 2 minutes left. Then light the unburned end of Fuse B while it's still burning in the middle and it should burn out in 1 minute, totalling 3 minutes in all. The only question I have is if this solution requires 2 identical fuses of even burn time, or if it will work as stated in the problem, 2 different fuses with uneven burn rates. I'll try to find a mathematical solution and edit later
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### #5 bonanova

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Posted 20 October 2007 - 05:33 AM

I think you light one fuse (Fuse A) on both ends and Fuse B on one end simultaneously. Once Fuse A has completely burned to the middle, 2 minutes have passed. Fuse B should have also burned for 2 minutes, so it will have 2 minutes left. Then light the unburned end of Fuse B while it's still burning in the middle and it should burn out in 1 minute, totalling 3 minutes in all. The only question I have is if this solution requires 2 identical fuses of even burn time, or if it will work as stated in the problem, 2 different fuses with uneven burn rates. I'll try to find a mathematical solution and edit later

No it doesn't.
All they need to do is burn completely in the specified time.
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The greatest challenge to any thinker is stating the problem in a way that will allow a solution.
- Bertrand Russell

### #6 Taidaishar

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Posted 02 November 2007 - 07:09 PM

You want to boil a perfect 3-minute egg.

For a timer, you have only two 4-minute fuses, that do not burn at an even rate.

Can you have breakfast without a runny [or overly hard] egg?

I didn't read any of the solutions or spoilers before this, so this will be going from scratch:

Light both fuses, one from both ends and one from one end. When the one that you lit from both ends burns out, 2 minutes will have elapsed. At that point, 2 minutes will have burned off of the other fuse also leaving 2 minutes to burn. Now, light the OTHER fuse from the other end and the 2 minutes that are left will burn in 1 minute giving you a total of 3. YAY!
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### #7 rookie1ja

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Posted 02 November 2007 - 07:30 PM

nice ... the same principle is applied in the following brain teaser called Igniter Cords

and if you like that type of puzzles, be sure to check the following pouring water and weighing puzzles
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