12 Balls Puzzle

[PDad]

I was reminded of a good puzzle I solved a long, long time ago in HS. Let's see whom here can solve it.

You have 12 balls numbered 1-12 that otherwise appear and feel identical, except one is either slightly heavier or lighter than the other 11 (you can't feel it). Using only a balance scale w/o weights, how do you identify the odd ball and whether it is heavier or lighter than the others with only 3 weighings on the scale?

[Battle]

I was reminded of a good puzzle I solved a long, long time ago in HS. Let's see whom here can solve it.

You have 12 balls numbered 1-12 that otherwise appear and feel identical, except one is either slightly heavier or lighter than the other 11 (you can't feel it). Using only a balance scale w/o weights, how do you identify the odd ball and whether it is heavier or lighter than the others with only 3 weighings on the scale?

I would be honored to take the 1st stab....

Half and weigh 6 on each side. Which ever side is lighter, you half and weight 3 on each side. Whichever one is lighter, you weigh one on each side. If they weigh the same then the one left over is the light ball

[PDad]

Battle's method would work if the odd ball was only lighter. However, the odd one is either heavier or lighter and you need to determine which it is.

[Battle]

Battle's method would work if the odd ball was only lighter. However, the odd one is either heavier or lighter and you need to determine which it is.

LOL...Oh yeah...I was rushing to solve and missed the 'heavier'..Dang it!

[Battle]

If you weigh 8 balls and remove 2, would that constitute a 2nd weighing?

[aparent]

Weigh 6 on each side, then swap three balls from one to the other. Depending on how the scale responds you will have narrowed it down to three balls and you will know if it is lighter or heavier that you are looking for. Then weigh two of balls. Either the scale will tell you which one is the right one or it will be in your hand.

What's my prize?

[PDad]

If you weigh 8 balls and remove 2, would that constitute a 2nd weighing?

Yes

[aparent]

Never mind...I'm an idiot my solution is flawed...the shame

[PDad]

Never mind...I'm an idiot my solution is flawed...the shame

No shame - it's a tough problem.

[Safebyahare]

I was reminded of a good puzzle I solved a long, long time ago in HS. Let's see whom here can solve it.

You have 12 balls numbered 1-12 that otherwise appear and feel identical, except one is either slightly heavier or lighter than the other 11 (you can't feel it). Using only a balance scale w/o weights, how do you identify the odd ball and whether it is heavier or lighter than the others with only 3 weighings on the scale?

Place the one ball on the scale. Place the three ball on the other side.
The one ball is either slightly heavier or slightly lighter, and three is only weighing on scale.
Drink.