Do you like riddles?

**bivonic** · 03-16-2003, 04:03 PM

This is my favorite, not a trick question:

There are 2 pieces of string. Each piece is made of a different material and are of different lengths. Both pieces of string take exactly 1 hour to burn from one end to the other end. The speed of burning is not
uniform throughout. So, it can burn quickly first, then slowly at the end, or any random way. If you are given only these two pieces of string and a box of matches, how do you measure 45 minutes?

The solution only requires you to burn the strings. No other actions like cutting, measuring, etc. is involved

This problem was set up by a professor for a PH.D qualifying examination at Stanford University. They are expected to answer it in 15 mins.

Good luck....

**Briela** · 03-16-2003, 04:21 PM

Since each string burns for 1hr, light 1 string at both ends and it will burn for 30 min. At the same time, light just one end of the other. Once the first burns all the way, light the other end of the second and the remaining burning of that one should take 15 minutes... a total of 45 minutes.

Do I get to go to Stanford now? [img]/ubbthreads/images/icons/smile.gif[/img]

**DONOTDELETE** · 03-16-2003, 07:11 PM

\"How do you measure 45 minutes?\"

By looking at your watch while you burn the strings.

**Phantom** · 03-16-2003, 07:19 PM

Given: String A and B and box of matches (more than 2)
Assume: The time taken to burnt the string is 1 hr from either end.
Steps:
1) Burn 2 ends of String A and just 1 end of String B at the same time
2) When String A is fully burnt, the time taken should be 30 mins (may
not end at mid-point)
3) Now burnt another end of String B (both ends are burnt), until the
remaining of String B is fully burnt. The time taken is 15 mins
(1/2 of 30 mins).
4) So, total time spent = 30+15 = 45mins!
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lol I stole that from a website [img]/ubbthreads/images/icons/tongue.gif[/img]

**Phantom** · 03-16-2003, 07:25 PM

I dont like riddles anyways.... who would spend there time watching 2 pieces of string burn into ash? probably a really big loser or a pyromaniac.... I like watching girls in G strings though, 2 of them is even better [img]/ubbthreads/images/icons/laugh.gif[/img]

**Phantom** · 03-16-2003, 07:33 PM

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**bundyburger** · 03-17-2003, 01:36 AM

ooooo ...that\'s a great butt! [img]/ubbthreads/images/icons/tongue.gif[/img]

[img]/ubbthreads/images/icons/laugh.gif[/img] [img]/ubbthreads/images/icons/laugh.gif[/img] [img]/ubbthreads/images/icons/laugh.gif[/img] [img]/ubbthreads/images/icons/laugh.gif[/img]