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Fuse on fire

I do not like the answer to this puzzle as fuses are not used to measure time. They are used to let the bomber to get as far as possible from the bomb before it explodes. So if the bomber has a watch, he does not need to waste a fuse - he could just wait another 15 seconds before firing the other fuse. If he does not have a watch, how does he know when to fire the first fuse?

Is that right?

vk
Wednesday, November 19, 2003

You are right about the problem being highly contrived. However, the problem is still just about using the fuses to measure 45 seconds...even though the context under which it is being done is rather foolish.

James Kloberdance
Wednesday, November 19, 2003

Accepted. But in this case I would restate the problem for the future generations.

A mad bomber wants to cook a poached egg for his Sunday breakfast. According to the recipe he needs to “break an egg into a pot with boiling salted water and keep it there for only 45 seconds”. Unfortunately to time this process he has two fuses (pieces of string) of varying thickness which each burn for 30 seconds. He can't cut the one fuse in half because the fuses are of varying thickness and he can't be sure how long each half will burn. How can he arrange the fuses to make his breakfast right?

vk
Thursday, November 20, 2003

There's a certain amount of trust you have to have that a problem is as it seems, and this violates that trust.  It should go without saying that if the guy wants a 45 second fuse for his bomb it's got to be 45 seconds in one shot.

This problem just detracts from all the rest.  There are a lot of tough problems here that have legitimate answers.  That's what I thought I was dealing with so I ended up wasting a lot of time on this problem.  Now any time I'm stuck on a hard problem I'm tempted to peak at the answer to make sure I'm not wasting my time on another wild fuse chase.

Bill Hees
Sunday, November 23, 2003

The question does'nt have any problem. but the answer should be like this:
Tie one end of the fuse to the mid point of the other fuse forming a 'T' shape, attach the bomb to the lower end and fire 2 ends of the upper fuse. now u can run before it takes 45 seconds for the bomb to get blasted.

vijayakumar b
Tuesday, January 06, 2004

Hello there,

I do not agree with your solution as you cannot be sure that both ends of the fuse meet in the middle.

Imagine the left side burns down in 5 seconds and the right side in 25.
Lets do a test with your answer:
the second fuse would be set on fire after 5 seconds when the first one reaches the middle of the fuse.
25 seconds later the first fuse is smoked up
-> 30 sec
and again 5 seconds later you can measure
35 seconds.
therefore this answer is only correct if at least one fuse burns with a constant speed.
mfg

Philipp Bader
Tuesday, January 13, 2004

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