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More ways to get Braingle...

Odd Ball

Logic puzzles require you to think. You will have to be logical in your reasoning.

 

Puzzle ID:#2295
Fun:*** (2.12)
Difficulty:*** (2.64)
Category:Logic
Submitted By:tommo***
Corrected By:cnmne

 

 

 



You are given 14 balls, one of which is marked as a reference ball. 12 of the other balls are the same weight as the reference ball but the other ball may be slightly heavier, slightly lighter or the same weight as the reference ball. Using a balance scale how can you determine which is the odd ball, if any, with just three weighings?




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Comments

absy*us*
Dec 06, 2003

omg just looking at the explanation made my head hurt.
froggyggAus*
May 24, 2005

Good teaser...even though the answer "rolled" right past me!
Knew it had something to do with splitting them into groups, but not quite sure how. Stumped me.
thompson1Aus*
Feb 22, 2006

The groups are 4,4, and 5, so there can't be 2 groups of 5 to weigh against each other
tintiniscoolAus*
Oct 10, 2006

............. ................
dudebomb93Aus*
Jul 27, 2007

that was so stupid boring and dumb,i mean its not fun when its complicating,i mean the freekin answer is complicating
tommo
Sep 16, 2009

There ARE two groups of 5 balls.
On is 5 unknown balls. Tne other is 4 unknown plus the reference (4+1 =5)
daveyfitz
Apr 10, 2015

This is solvable without the reference ball. 1st weighing: 4 vs 4. Result A: they balance. Weigh 3 of the remaining 5 against 3 of the 8 we now know are normal. If it is unbalanced, we now know if the strange ball is heavy or light, and its in the 3, so weigh two of them against each other to find the one. If they balance, its in the two we haven't weighed, weigh one of them against one of the normal ones. Result B: One side of the 4v4 is heavy. So, we have 5N (the normal, unweighed ones), 4H from the heavy side, and 4L from the light side. Weigh 2H+1L vs 1H+1L+1N. If the first side goes heavy, its in the 2H, or the 1L on the other side. Weigh the 2H against each other to see which. If the first side goes light, its the 1L on the first side or the 1H on the second side, weigh one of them vs 1N to decide. If the scale balances, its among the 1H and 2L we didn't weigh. Weight the 2L against each other to see which.



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