 |  |  |  |  |  |  |  |
Billiard Ball Problem
 |
•
•
Join Date: Oct 2007
Posts: 52
Reputation: 
Solved Threads: 0
Junior Poster in Training
You have 9 billiard balls. They are all the same weight, save one. You want to find out which one is heavier. All you have is a scale that determines the heavier side. You can weigh any number of balls at any time. What is the least amount of weighings you can do to find the heaviest ball?
•
•
Join Date: Jan 2008
Posts: 3,829
Reputation: 
Solved Threads: 501
•
•
•
•
Originally Posted by weasel7711 
You have 9 billiard balls. They are all the same weight, save one. You want to find out which one is heavier. All you have is a scale that determines the heavier side. You can weigh any number of balls at any time. What is the least amount of weighings you can do to find the heaviest ball?
Edit - I explained how, but after thinking about it, I took down the explanation in case other people want to puzzle over it themselves.
As a generalization, if you have n balls and one of them is heavy, how many weighings does it take?
Last edited by VernonDozier; Apr 1st, 2009 at 4:43 pm.
•
•
Join Date: Mar 2009
Posts: 62
Reputation:
Solved Threads: 0
Junior Poster in Training
correct me if im wrong (and might be the case) but if you got 9 billiard balls all of the same weight wouldnt the answer be 0 : none would be hevier as they weigh the same??
•
•
Join Date: Jan 2008
Posts: 3,829
Reputation:
Solved Threads: 501
•
•
•
•
Originally Posted by chriswellings
correct me if im wrong (and might be the case) but if you got 9 billiard balls all of the same weight wouldnt the answer be 0 : none would be hevier as they weigh the same??
•
•
•
•
You have 9 billiard balls. They are all the same weight, save one. You want to find out which one is heavier.
•
•
Join Date: Mar 2009
Posts: 62
Reputation:
Solved Threads: 0
Junior Poster in Training
lol... i read the q over and over mabee the question shoulda been worded a little different say they all weight the same excep one??
•
•
•
•
Originally Posted by VernonDozier
Cool problem. You can do it in two weighings.
Edit - I explained how, but after thinking about it, I took down the explanation in case other people want to puzzle over it themselves.
As a generalization, if you have n balls and one of them is heavy, how many weighings does it take?
Never approach a computer with the words "I'll just do this quickly..."
•
•
Join Date: Jan 2008
Posts: 3,829
Reputation:
Solved Threads: 501
•
•
•
•
Originally Posted by Thinka
I've been thinking about it, and I can't work it out. Pray tell, what be the answer?
So after one weighing, you've narrowed it down to one of three balls. Randomly pick two of the three balls. Stick one ball on each side of the scale. Weigh them. If they weigh the same, the heavy ball is the ball that isn't on the scale. If one ball on the scale is heavier than the other, that's the heavy ball.
|
Similar Threads
- Nuclear Power (Geeks' Lounge)
Other Threads in the Geeks' Lounge Forum
- Previous Thread: What is Generic Viagra?
- Next Thread: Space suggestions.
| Thread Tools | Search this Thread |
You need to join our community in order to build your list of favorite forums. You can visit the forum index for a listing of all forums.
Latest Geeks' Lounge Posts
- Today's Posts
- Unanswered Threads
Related Forum Features
article bankrupt bankruptcy bear beard beijing bot children code cognitive_disorder complaint console consoles convert cracked.com daniweb design development election empty facebook feed financialcrisis fun games gaming garbage google grandtheftauto gta hardware hunting internet java kindle king knife library life linux mad manly marketing mars merger microsoft ms murder netbook networking news nintendo odf office operating opinion os pain parentalcontrol parenting planning playstation population ps3 ps4 python rss school security sims software sony source study subversion survey systems tablet thelostanddamned thing timeisonmyside. unsolved unused usarmy vapid videogames viruses wakoopa wave wii windows windows>all windows_wins world worldofwarcraft wow www xbox xbox360 zomg_conspiracy
