6 replies to this topic

[bonanova]

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?

[Writersblock]

I think that

Spoiler for solution

For the fuses to burn at 4 minutes, even if they are not evenly burning fuses, they will have to burn at basically the same rate regardless of which side you light. If this wasn't the case, you couldn't count on them being 4 minute fuses. So you can't just eyeball 1/2 way and count that as 2 minutes because they don't burn evenly, but you can expect that if you light both sides, you can expect a 2 minute burn time. So I light fuse 1 on both sides and fuse 2 on one side. As soon as fuse 1 is expired, I light the other end of fuse 2, giving me a one minute burn time on the remaining fuse, which is a 3 minute total burn. As soon as fuse 2 is expired, I take off my egg and let it cool a bit. Then I crack it and enjoy it with a muffin and some salt. Yum. Perfect 3 minute egg.

[aforsy]

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

[slmo]

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

[bonanova]

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.

[Taidaishar]

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!

[rookie1ja]

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