Sunday, November 12, 2006

New Puzzle

Some of you had some interesting responses to my last puzzle. Several of you (rightly) chose to not post your answer publicly, but instead emailed them to me. And so I've decided to backstep a bit, and to offer a more deterministic puzzle. This is better suited for those who not only wish to remain inside the box, but also want to be reminded of where the box's walls are.

Puzzle:
You have eight billiard balls. One of them is defective in that it weighs more than the others. How do you tell, using a balance, which ball is defective in only two weighings?

While it's probably possible to google the answer. Please give it an honest try on your own.

5 comments:

Joe said...

Don't try to weigh them at all. Just hit them really low and pop them off the table. The heavier ones will make larger holes in the wall.

Michael said...

I like Joe's idea. I received an email answer that involved firing bullets at the balls. LOL

michael said...

I need to announce, that Jason was the first with the correct answer. Although he does get 1 demerit for emailing it, insteal of displaying his prowess by posting the answer.

The answer is (and reportedly, there is only 1 answer): set 2 balls aside, then balance the remaining 6 balls as 3 vs 3. If they balance, then the second weighing will involve 2 balls set aside (which will discover the heavy ball). If they don't balance, then weighing any 2 of the 3 balls that are heavier should do the trick. If you need the last steps described in detail, then you should be visiting other blogs.

Michael said...

I apologize for the typos in the above note. I can't seem to find the means (if it exists) to edit comments. hmmmm

So I think i'll just retire to a beer and watch The Simpsons.

Jason said...

The key with this is to maximize the information gained from each weighing....by leaving balls out, you learn about those balls, either isolating the heavy one or identifying it...