Liberal Forum

DeezerShoove » 26 Aug 2022, 7:46 pm » wrote: ↑

26 Aug 2022, 7:46 pm

I am with you for the first step.
4x4 gets you a control group (or two if they balance).
The remaining odd four are easy to sort in two weighings.

If the first 4x4 do not balance, isn't this where the "solution" and actually the problem really is?

How do you find 1 odd ball out of 8 in just two weighings?

Exactly.

I have solved it in just two weighings under that condition, but only when replacing 2 marbles from side a and one from side b with control marbles results in an even weighing. I can work it in a single weighing from there. But that is only going to happen 3/8ths of the time. And you will get an even weighing on the original 4x4 only 1/3rd of the time. So it's just over a 70% solution under my scheme. 

But if the second weighing is still not even, I cannot work it in a single weighing from there. I need two. So I am either incorrect in my second step, or unable to figure out my last step properly in the event of an odd weighing. 

If the second weighing is still odd, that means I have 5 suspect marbles - 3 on one side and two on another. If there's a way to find the suspect in a single move, it sure as hell isn't one I can find. Which makes me think my second step is a half measure in the first place.