Fuse Timer Puzzle

[pdurrant]

Originally Posted by dreams

I couldn't figure this one out. I was able to start, but once again was lost.

Spoiler:

I had the control candle burning as I used subsequent candles and stopped and started them at various points related to the control candle. But I still couldn't get a way to figure out exact timing.

Hint: They are not candles, they are fuses.
Clue:

Spoiler:

Fuses have two ends.

[dreams]

Originally Posted by pdurrant

Hint: They are not candles, they are fuses.
Clue:

Spoiler:

Fuses have two ends.

Well, if I would have known that (spoiler) difference, it would have changed everything.

So now...

Spoiler:

I can light them at both ends!

I'll see if I can work with that new-to-me information when I get home tonight. Thanks!

[pdurrant]

Originally Posted by dreams

Well, if I would have known that (spoiler) difference, it would have changed everything.

So now...

Spoiler:

I can light them at both ends!

Exactly so. I don't think it's possible to solve it without that info.

[omk3]

Originally Posted by dreams

Well, if I would have known that (spoiler) difference, it would have changed everything.

So now...

Spoiler:

I can light them at both ends!

I'll see if I can work with that new-to-me information when I get home tonight. Thanks!

Don't worry dreams, I didn't think they were candles, and still it took me more time than it should to realise that simple, in afterthought, fact.

You're really close now!

[zelda_pinwheel]

new puzzle, yay !! okay, here is my idea :

Spoiler:

i presume that these fuses are not encased in anything and you have access to then entire fuse (including both ends). if this is true :

you need 3 4-minute fuses for your egg.

you light 3 of them at the same time ; the first one, you light at both ends.

since it is burning from both ends, it should burn twice as fast, therefore when it is completely consumed you know 2 minutes have passed.

when the first fuse has burned, you light the second end of the second fuse ; it should have 2 minutes left to burn, but now burning from both ends it will burn in 1 minute.

when the second fuse has completely burned, 3 minutes have passed, and the last fuse should have 1 minute left to burn. you light the second end of that fuse, and it will now burn twice as fast, and when it is burned a total of 3 and a half minutes has elapsed.

very work-intensive for one egg but some people are so *particular* about that.

okay, now for the spoiler tags !!! am i right ? am i right ??

[zelda_pinwheel]

woo hoo ! i have the same answer as omk, who is right. so i'm right too ! great puzzle paul !!

[omk3]

Woohoo! Congratulations Zelda!

[zelda_pinwheel]

thanks ! these are really fun.

[pdurrant]

Originally Posted by zelda_pinwheel

am i right ? am i right ??

Yes, you are exactly right. Congratulations!

[LazyScot]

Spoiler:

Take two fuses. Lay them out parallel.

Light one from one end, and the other from the other end.

Extinguish when the burn points of the two "meet" somewhere along the line.

You must now have two two minute fuses.

Now lay those two in parallel.

Light one from one end and one from the other end.

Extinguish when the burn points of the two "meet" somewhere along the line.

You now must have two one minute fuse.

Now lay those two in parallel.

Light one from one end and one from the other end.

Extinguish when the burn points of the two "meet" somewhere along the line.

You now have two 30 second fuses.

Take one of the four minute fuses, and light it, and light the 30 second fuse at the same time.

When the 30 second fuse goes out, either extinguish the four minute fuse to give you a 3:30 fuse, or put your eye into the boiling water (you did remember to start the water boiling, didn't you?).

And if extinguishing is impossible, you should be able to "move" the fuses that are burning....

Correct?

This only needs 3 fuses....

[pdurrant]

Originally Posted by LazyScot

Spoiler:

Take two fuses. Lay them out parallel.

Light one from one end, and the other from the other end.

Extinguish when the burn points of the two "meet" somewhere along the line.

You must now have two two minute fuses.

Now lay those two in parallel.

Light one from one end and one from the other end.

Extinguish when the burn points of the two "meet" somewhere along the line.

You now must have two one minute fuse.

Now lay those two in parallel.

Light one from one end and one from the other end.

Extinguish when the burn points of the two "meet" somewhere along the line.

You now have two 30 second fuses.

Take one of the four minute fuses, and light it, and light the 30 second fuse at the same time.

When the 30 second fuse goes out, either extinguish the four minute fuse to give you a 3:30 fuse, or put your eye into the boiling water (you did remember to start the water boiling, didn't you?).

And if extinguishing is impossible, you should be able to "move" the fuses that are burning....

Correct?

This only needs 3 fuses....

No, sorry that doesn't work.

Spoiler:

The fuses burn at an uneven rate (stated in the question). This means (in extreme cases) that one might burn 1/3 of its length in 1 minute, the next 2/3 in three minutes. Another might burn 2/3 of its length in 1 minute and the next 1/3 in three minutes. Your scheme of extinguishing when the burn points meet would give you a three minute fuse (in this case) not a two minute fuse. And that's without considering that the fuses might not be the same physical length... although I admit that isn't explicitly stated in the question.

Do have another go!

[pdurrant]

I won't be posting the answer to this puzzle until tomorrow morning (UK time).

I will then be posting another puzzle. That puzzle will involve a desert, an oasis, and a limited ability to carry water....

[zelda_pinwheel]

Originally Posted by pdurrant

Yes, you are exactly right. Congratulations!

yay ! thanks for the puzzle ! i can't wait for the next one. an oasis you say ? hm...

[dreams]

It's fun trying to do these with others.

My guess.

Spoiler:

Now, that I know that a fuse can be lit at both ends..

Also, that if I lit 3 fuses, (let them burn for a little, then blew them out), that they would have burned differing percentages of each fuse. They would only match if let to burn completely.

So.. Put the egg in boiling water and...

F1 lite both ends and F2 & F3 light one end each

F1 is consumed [in 2 minutes as twice as fast]

F2 has burned for 2 min, so lite other end of F2 (to burn up 2 min in only 1 min).

F2 is consumed in 1 minute [twice as fast]

F3 has been burning for 3 minutes (1 min left), so lite the other end..

F3 is consumed in 30 sec [twice as fast]

F3 burned for 3 min and 30 sec.

Remove egg and enjoy.

Thanks! I love trying to figure these out. I'm looking forward to the next one.

[obs20]

I couldn't get it either. The heat down here has been frying my brain. The Temperature Humidity Index today was 103.
This whole week I've just been too beat to think.
I need a drink.