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View Full Version : Puzzle: Twelve Billiard Balls

JanT
13 Dec 2007, 18:49
In Psychology today, we were given Piaget's Twelve Billiard Balls puzzle to sort out. Why? Ask me another. Surely this would be a Maths problem.


The Twelve Billiard Balls Puzzle

There are twelve billiard balls, all the same size, shape and colour. All weigh exactly the same, except that one ball is slightly different in weight, but not noticeably so in the hand. Moreover, the odd ball might be lighter or heavier than the others.

Your challenge is to discover the odd ball and whether it is lighter or heavier. You must use a beam balance only, and you are restricted to three weighing operations.


Solution here. (http://www.bikwil.com/Vintage06/Billiard-Ball-Puzzle.html#Article)
R.
13 Dec 2007, 20:35
:sherlock:
Cpl Mickey
14 Dec 2007, 18:44
:sherlock:

I'll go along with that thought R
Lord Kagan
14 Dec 2007, 18:48
surely an easier way would be to counter balance each ball on the beam balance and whatever one isnt balanced contains the heavier/lighter ball by process of elimination?
Cpl Mickey
14 Dec 2007, 18:54
surely an easier way would be to counter balance each ball on the beam balance and whatever one isnt balanced contains the heavier/lighter ball by process of elimination?

That sounds too easy. lol !
samurai7
14 Dec 2007, 19:32
surely an easier way would be to counter balance each ball on the beam balance and whatever one isnt balanced contains the heavier/lighter ball by process of elimination?

yeah, but you're only allowed three weighing processes, and there are twelve balls, innit?
duke knooby
14 Dec 2007, 19:45
1st attempt.. 6 on each side
2nd attempt.. 3 on each side
3rd attempt.. 1 on each side.. if balanced the un used ball is the odd one.

only re weigh the heavy side
AndyK
14 Dec 2007, 19:55
1st attempt.. 6 on each side
2nd attempt.. 3 on each side
3rd attempt.. 1 on each side.. if balanced the un used ball is the odd one.

only re weigh the heavy side


What happens if the ball that is a different weight is lighter than the other 11?
duke knooby
14 Dec 2007, 20:04
good point... :?
mszee
14 Dec 2007, 21:13
Yeah, ok...I knew that one before...started reading from the link and remembered why I forgot it...

Well, I think lesson well learned here is that it's much worse without any balls...I think so anyway...
Lord Kagan
15 Dec 2007, 13:29
ill work my way out later... cant be fecked now