Re: Marbles, Just for fun...
4?
12 --/\-- 12 take the heavy side
6 --/\-- 6 take the heavy side
3 --/\-- 3 take the heavy side
1 --/\-- 1 if one side is heavy; thats the one: if they balance your extra one is heavy
Re: Marbles, Just for fun...
there's a better solution, give it a minute and the penny will drop.
Re: Marbles, Just for fun...
I am going to assume that you need to be able to determine it with 100% certainty? Otherwise, you could take two marbles at random, place them on the scale, and if you're very lucky you will have taken the heavier marble --> only one weigh required. The question doesn't really address this, but I don't think a solution like that is acceptable... Right? ;)
Re: Marbles, Just for fun...
Spoiler Warning (highlight the text with your mouse to read it)
Weigh 8v8 [8 left out]; if they balance throw them out, if they don't take heavier side.
3v3 [2 left out]; if they balance throw them out; if they don't take heavier side.
1v1, possibly with one left out; take heavier side; if one is left out and they balance, take that one.
3 :)
Re: Marbles, Just for fun...
jemidiah, you got it. (again)
If you think the puzzle worth it maybe edit your post.
:)
Re: Marbles, Just for fun...
Hint
(if anybody's particularly interested without getting the answer) 24 is divisible by both 2 and 3. The 3 is important.
Re: Marbles, Just for fun...
Quote:
Originally Posted by
jemidiah
Spoiler Warning
I hope you don't mind, I changed the text colour of your solution so that it can't be read accidentally. :)
Re: Marbles, Just for fun...
What I like about this problem is that the number of measurements required to determine the culprit for N marbles goes by the power of 3. So, if it takes M measurements to figure it out for N marbles in one instance it takes M + 1 measurements to figure out for 3 * N marbles.
Re: Marbles, Just for fun...
Quote:
Originally Posted by
si_the_geek
I hope you don't mind, I changed the text colour of your solution so that it can't be read accidentally. :)
Good idea :thumb:
Re: Marbles, Just for fun...
I say zero.
If you gently shake the bag of marbles for a while, then the heavier marble will slowly settle to the bottom.