Register Guidelines E-Books Search Today's Posts Mark Forums Read

Go Back   MobileRead Forums > Miscellaneous > Lounge

Notices

Reply
 
Thread Tools Search this Thread
Old 06-23-2010, 12:59 PM   #1
pdurrant
The Grand Mouse
pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.
 
pdurrant's Avatar
 
Posts: 31,667
Karma: 87823216
Join Date: Jul 2007
Location: Norfolk, England
Device: NOOK ST GlowLight
Fuse Timer Puzzle

This one's adapted from http://www.rinkworks.com/brainfood/p/discrete5.shtml

You like your boiled eggs to be boiled for exactly three-and-a-half minutes.

Unfortunately, you've broken your three-and-a-half minute egg timer, and the only other timing mechanism in the house are some slow-burning four minute fuses*. NB. I mean fuses that burn for exactly four minutes, not four fuses that burn for a minute each!

Unfortunately (again), you know that the fuses do not burn at a uniform rate, so you can't just cut one of them to a three-and-half minute length.

Can you time exactly three-and-a-half minutes for your egg using the four minute fuses? If so, how?

Oh - and spoiler tags around answers please. Many thanks to all of you who remembered without me reminding you.


*No, I don't know why you have four-minute fuses in the house either. And yes, you do have some matches as well.

Last edited by pdurrant; 06-23-2010 at 02:12 PM. Reason: Forgot the spoiler tags reminder
pdurrant is offline   Reply With Quote
Old 06-23-2010, 01:33 PM   #2
clarknova
Addict
clarknova plays well with othersclarknova plays well with othersclarknova plays well with othersclarknova plays well with othersclarknova plays well with othersclarknova plays well with othersclarknova plays well with othersclarknova plays well with othersclarknova plays well with othersclarknova plays well with othersclarknova plays well with others
 
clarknova's Avatar
 
Posts: 242
Karma: 2617
Join Date: Mar 2009
Location: Greenwood, SC
Device: Kindle 2
Spoiler:
Wouldn't you just light the first three fuses in succession to count three minutes, and then the fourth fuse at both ends to get it to burn for only 30 seconds?


I'd probably end up contacting the Chinese manufacturer of these timing fuses to figure out what math they used to calculate these non-uniform fuses' burn times.
clarknova is offline   Reply With Quote
Old 06-23-2010, 01:35 PM   #3
HarryT
eBook Enthusiast
HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.
 
HarryT's Avatar
 
Posts: 63,364
Karma: 41542799
Join Date: Nov 2006
Location: UK
Device: PW2, iPad Retina Mini, iPhone 4, MS Surface Pro, Onyx T68, N7,
Quote:
Originally Posted by clarknova View Post
Spoiler:
Wouldn't you just light the first three fuses in succession to count three minutes, and then the fourth fuse at both ends to get it to burn for only 30 seconds?


I'd probably end up contacting the Chinese manufacturer of these timing fuses to figure out what math they used to calculate these non-uniform fuses' burn times.
Spoiler:
I think Paul means that you have "fuses that burn for four minutes", rather than "four one minutes fuses" .
HarryT is online now   Reply With Quote
Old 06-23-2010, 01:40 PM   #4
clarknova
Addict
clarknova plays well with othersclarknova plays well with othersclarknova plays well with othersclarknova plays well with othersclarknova plays well with othersclarknova plays well with othersclarknova plays well with othersclarknova plays well with othersclarknova plays well with othersclarknova plays well with othersclarknova plays well with others
 
clarknova's Avatar
 
Posts: 242
Karma: 2617
Join Date: Mar 2009
Location: Greenwood, SC
Device: Kindle 2
Quote:
Originally Posted by HarryT View Post
Spoiler:
I think Paul means that you have "fuses that burn for four minutes", rather than "four one minutes fuses" .
Ahh... I see. I re-read, and it seems you're correct.
clarknova is offline   Reply With Quote
Old 06-23-2010, 01:41 PM   #5
omk3
Wizard
omk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five words
 
omk3's Avatar
 
Posts: 1,454
Karma: 37243
Join Date: Dec 2009
Location: Europe
Device: pocketbook 360, kindle 4
Okay, after looking at this for some time thinking it can't be possible, or that I'm missing some special physics of fuses , here's my idea:

Spoiler:
We take 3 fuses and light them all at the same time.
We light fuse A from both ends. This should make the fuse burn in half the time, ie 2 minutes.
We have lit fuse B from one end only, but on the 2 minute mark, when A is burned, we light the other end of B too. The time remaining on B was two minutes. Now, with both ends lit, it will burn completely in one minute. We are now on our third minute.
We have lit fuse C from one end only, but on the 3 minutes mark, when B is completely burned, we light the other end of C too. The time remaining for C to burn completely would be 1 minute. Because it is burning from both ends, it will take half the time, so it will burn in half a minute.
When C is completely burned, we are at exactly 3 and a half minutes from when we started.
omk3 is offline   Reply With Quote
Old 06-23-2010, 01:44 PM   #6
HarryT
eBook Enthusiast
HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.HarryT ought to be getting tired of karma fortunes by now.
 
HarryT's Avatar
 
Posts: 63,364
Karma: 41542799
Join Date: Nov 2006
Location: UK
Device: PW2, iPad Retina Mini, iPhone 4, MS Surface Pro, Onyx T68, N7,
Quote:
Originally Posted by omk3 View Post
Okay, after looking at this for some time thinking it can't be possible, or that I'm missing some special physics of fuses , here's my idea:

Spoiler:
We take 3 fuses and light them all at the same time.
We light fuse A from both ends. This should make the fuse burn in half the time, ie 2 minutes.
We have lit fuse B from one end only, but on the 2 minute mark, when A is burned, we light the other end of B too. The time remaining on B was two minutes. Now, with both ends lit, it will burn completely in one minute. We are now on our third minute.
We have lit fuse C from one end only, but on the 3 minutes mark, when B is completely burned, we light the other end of C too. The time remaining for C to burn completely would be 1 minute. Because it is burning from both ends, it will take half the time, so it will burn in half a minute.
When C is completely burned, we are at exactly 3 and a half minutes from when we started.
Spoiler:
That looks right, but one can't help thinking that it would be a lot easier just to look at your watch.
HarryT is online now   Reply With Quote
Old 06-23-2010, 01:46 PM   #7
omk3
Wizard
omk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five words
 
omk3's Avatar
 
Posts: 1,454
Karma: 37243
Join Date: Dec 2009
Location: Europe
Device: pocketbook 360, kindle 4
Quote:
Originally Posted by HarryT View Post
Spoiler:
That looks right, but one can't help thinking that it would be a lot easier just to look at your watch.
Where's the fun in that?
omk3 is offline   Reply With Quote
Old 06-23-2010, 02:13 PM   #8
pdurrant
The Grand Mouse
pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.
 
pdurrant's Avatar
 
Posts: 31,667
Karma: 87823216
Join Date: Jul 2007
Location: Norfolk, England
Device: NOOK ST GlowLight
Quote:
Originally Posted by clarknova View Post
Spoiler:
Wouldn't you just light the first three fuses in succession to count three minutes, and then the fourth fuse at both ends to get it to burn for only 30 seconds?


I'd probably end up contacting the Chinese manufacturer of these timing fuses to figure out what math they used to calculate these non-uniform fuses' burn times.
Sorry, the fuses each burn for four minutes, not one minute. Question changed to emphasise that each individual fuse burns for four minutes.
pdurrant is offline   Reply With Quote
Old 06-23-2010, 02:14 PM   #9
pdurrant
The Grand Mouse
pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.
 
pdurrant's Avatar
 
Posts: 31,667
Karma: 87823216
Join Date: Jul 2007
Location: Norfolk, England
Device: NOOK ST GlowLight
Quote:
Originally Posted by omk3 View Post
Okay, after looking at this for some time thinking it can't be possible, or that I'm missing some special physics of fuses , here's my idea:

Spoiler:
We take 3 fuses and light them all at the same time.
We light fuse A from both ends. This should make the fuse burn in half the time, ie 2 minutes.
We have lit fuse B from one end only, but on the 2 minute mark, when A is burned, we light the other end of B too. The time remaining on B was two minutes. Now, with both ends lit, it will burn completely in one minute. We are now on our third minute.
We have lit fuse C from one end only, but on the 3 minutes mark, when B is completely burned, we light the other end of C too. The time remaining for C to burn completely would be 1 minute. Because it is burning from both ends, it will take half the time, so it will burn in half a minute.
When C is completely burned, we are at exactly 3 and a half minutes from when we started.
Yes, exactly right! Well done.
pdurrant is offline   Reply With Quote
Old 06-23-2010, 02:15 PM   #10
pdurrant
The Grand Mouse
pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.
 
pdurrant's Avatar
 
Posts: 31,667
Karma: 87823216
Join Date: Jul 2007
Location: Norfolk, England
Device: NOOK ST GlowLight
Quote:
Originally Posted by HarryT View Post
Spoiler:
That looks right, but one can't help thinking that it would be a lot easier just to look at your watch.
But no, no watches or other timing mechanisms are available.

You really ought to give your own answer before reading the spoilers — much more fun!
pdurrant is offline   Reply With Quote
Old 06-23-2010, 05:32 PM   #11
obs20
Wizard
obs20 ought to be getting tired of karma fortunes by now.obs20 ought to be getting tired of karma fortunes by now.obs20 ought to be getting tired of karma fortunes by now.obs20 ought to be getting tired of karma fortunes by now.obs20 ought to be getting tired of karma fortunes by now.obs20 ought to be getting tired of karma fortunes by now.obs20 ought to be getting tired of karma fortunes by now.obs20 ought to be getting tired of karma fortunes by now.obs20 ought to be getting tired of karma fortunes by now.obs20 ought to be getting tired of karma fortunes by now.obs20 ought to be getting tired of karma fortunes by now.
 
obs20's Avatar
 
Posts: 2,449
Karma: 26345744
Join Date: May 2010
Location: Florida
Device: Sony PRS 600, Nook ST, Toshiba Excite 10.1 AT 300
Am I along the right path?
Spoiler:
If I light a fuse at both ends it will bun for 2 minutes
obs20 is offline   Reply With Quote
Old 06-23-2010, 05:34 PM   #12
dreams
It's about the umbrella
dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.
 
dreams's Avatar
 
Posts: 25,118
Karma: 56218156
Join Date: Jan 2009
Device: Sony 505| K Fire | KK 3G+Wi-Fi | iPhone 3Gs |Vista 32-bit Hm Prem w/FF
I sure hope we have an unlimited supply of fuses, because I keep lighting them as I play with how to time subsequent burn rates.
dreams is offline   Reply With Quote
Old 06-23-2010, 05:35 PM   #13
omk3
Wizard
omk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five wordsomk3 can name that ebook in five words
 
omk3's Avatar
 
Posts: 1,454
Karma: 37243
Join Date: Dec 2009
Location: Europe
Device: pocketbook 360, kindle 4
Quote:
Originally Posted by obs20 View Post
Am I along the right path?
Spoiler:
If I light a fuse at both ends it will bun for 2 minutes
Yes
omk3 is offline   Reply With Quote
Old 06-23-2010, 05:42 PM   #14
pdurrant
The Grand Mouse
pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.pdurrant ought to be getting tired of karma fortunes by now.
 
pdurrant's Avatar
 
Posts: 31,667
Karma: 87823216
Join Date: Jul 2007
Location: Norfolk, England
Device: NOOK ST GlowLight
Quote:
Originally Posted by dreams View Post
I sure hope we have an unlimited supply of fuses, because I keep lighting them as I play with how to time subsequent burn rates.
You may have as many as you think you need.
pdurrant is offline   Reply With Quote
Old 06-24-2010, 04:13 AM   #15
dreams
It's about the umbrella
dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.dreams ought to be getting tired of karma fortunes by now.
 
dreams's Avatar
 
Posts: 25,118
Karma: 56218156
Join Date: Jan 2009
Device: Sony 505| K Fire | KK 3G+Wi-Fi | iPhone 3Gs |Vista 32-bit Hm Prem w/FF
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.
dreams is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Unutterably Silly Using an electronic timer lene1949 Lounge 15 09-11-2010 10:36 PM
Questions from iPad first-timer ficbot Apple Devices 13 05-31-2010 05:50 PM
Hello from an old new-timer ebuyer099 Introduce Yourself 1 05-21-2010 01:34 PM
First timer on this board... Robert Williams Writers' Corner 9 08-16-2009 01:43 PM
first timer ChrisM12743 Introduce Yourself 3 03-29-2008 11:35 AM


All times are GMT -4. The time now is 11:26 PM.


MobileRead.com is a privately owned, operated and funded community.