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Solution to previous day's puzzle:
First correct submission goes to Day[9]! GJ!
+ Show Spoiler [solution] +
You can think of the ants as walking right through each other instead of meeting and separating again. So the ants will walk through each other and fall off the log eventually. And the longest will take 100 second, and none can be longer than that.
So new puzzle:
You have 2 strings, the length of those strings are unspecified, and you have some matches.
Important properties of the strings:
-Each string, if you lit one tip on fire, will take exactly 60 minutes to burn to the other tip.
-Each string takes an undefined burn rate, for instance, it may take 5 minutes to burn the first half of it, but 55 minutes to burn the remaining half.
Your task:
You want to measure a time interval of 45 minutes, how will you do it with the 2 strings and the matches you have?
Other info:
The first to answer the question correctly will be mentioned in the next day's blog.
-Something to keep in mind though, please put ALL relevant writings that might hint to the answer in spoiler. I get this feeling that after Day[9]'s got the answer, everyone just given up trying to solve it for themselves, which isn't helping you guys getting smarter.
-Clarifications will be given as needed, as some of you might not be familiar with the general math assumptions that might be omitted in the prompt.
Again, gl hf!
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yay!
+ Show Spoiler +1. Start burning string 1 from both ends, and at same time start burning string 2 from one end.
2. When string 1 burns out, light the other end of string 2.
3. When string 2 burns out it is 45mins.
This works because:
-Burning from both ends makes the string burn twice as fast
-After string 1 burns it means 30 minutes has passed, so there must be 30 minutes left on string 2
-Lighting string 2 from both ends will then only last 15 minutes.
-30mins+15mins = 45mins
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Kau
Canada3500 Posts
+ Show Spoiler +
Light both ends of one string and one end of the other.
When the first one is all burnt up, that will have been 30 minutes, at which point you light up the remaining end of the second string.
When that one is finished burning up it will have been another 15 minutes.
Edit: darn you highways
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Yep, seen it before; good one though ;P
Haha so close Kau
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+ Show Spoiler +
If you burn a string from both ends, it takes half as long. So burn string 1 from both ends, that's 30 minutes. But if you also burn one end of string 2 as you start burning string 1, string 2 will have half an hour of burning left.
So when string 1 is fully burned, light the other end of string 2 on fire. 30/2=15, 30+15=45.
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O dang nice time differences! Haha.
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DT> hydra ^ ^
edit, for comical value ^ ^
upgrade hydra speed next time
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seconds apart! oh snap, the FIRST reply got it too
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blargh i didn't get to answer!!! but i already knew this one lol
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I heard this before, but I did some major brainstorming the first time I saw it. Anyway, the correct answer was already given.
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GOT IT
+ Show Spoiler +since each string takes 60min to burn if u burned a string from both sides it will take 30 min to burn completely
so wat u do is u burn one string on both sides and u burn the other string on one side...
and once the string burning on both sides and finished burn up the other string will have exactly 30min of burn time left
u then quickly burn the unburnt side of the other string (one w/ 30min left) and then sit and watch and be happy that u got ur 45min of burn time
haha
EDIT: damn it... third ans...
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you need to start asking stuff no less difficult than rocket science or nuclear physics questions...
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+ Show Spoiler + My first thought was fold string 1 in two, start burning at one "end" of the new string created (therefore measuring 30 minutes with that string) and fold string 2 twice (in 4) and burn that one from one end after the 1st string stopped burning, thus measuring 15 minutes with it. It comes down to the same thing as the previous answers though.
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On April 29 2009 01:29 EsX_Raptor wrote:
you need to start asking stuff no less difficult than rocket science or nuclear physics questions...
This is pretty much correct. All the questions that I asked in my blog got rocked within a few hours tops.
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Easy, I guess Highways gets it because he posted it first. Poor Kau.
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haha, this one was posted on the giant ass computer science white board a couple weeks ago in my department.
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Omg this is going to be an awesome series of blogs.
And  Kau.
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lol, i was up all night thinking that it would take 60 minutes to burn BOTH strings if one was tied to the end of the other and found a solution for that XD
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EPT
