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Four Weights (Posted on 2004-07-25) Difficulty: 3 of 5
You have 4 weights weighing 2,3,5 and 7 pounds. The problem is none of them are marked. What is the fewest number of weighings you need using a balance scale figure out which weights are which?

  Submitted by Brian Smith    
Rating: 3.5000 (8 votes)
Solution: (Hide)
Weighing#1 : 2 against 2; 7 weight always on heavy side

Weighing#2 : Compare the 2 from heavy side; isolates 7 weight

Weighing#3 : Compare 7lb against two weights:
If 7 is heavier than the two weights, the last weight is 5
If 7 is equal to the two weights, the last weight is 3
If 7 is lighter than the two weights, the last weight is 2

Weighing#4 : Compare the last two weights

Comments: ( You must be logged in to post comments.)
  Subject Author Date
SolutionPuzzle ResolutionK Sengupta2007-06-18 04:55:04
AnswerK Sengupta2007-06-18 04:53:25
my easy solutionAndy2005-05-01 17:01:12
mmmmmTaylor2005-04-09 23:42:58
re(2): My son's solutionBruce Brantley2004-12-30 12:45:22
Questionre: My son's solutionron2004-12-30 03:27:52
My son's solutionBruce Brantley2004-12-12 09:40:51
re. nitpickingHattie2004-11-24 18:53:58
nitpickingfoto2004-09-09 20:14:25
Some ThoughtsNo Subjectktii2004-08-30 04:46:15
Some ThoughtsSorting Networks.dhruv2004-08-23 11:54:45
four or fiveBruce Brantley2004-08-21 22:40:25
re(2): 2 weighings, re(4): done in 3 weighings.... I think =Pmauro schievano2004-08-10 08:20:17
re: 2 weighings, re(4): done in 3 weighings.... I think =PVina2004-07-28 03:16:45
2 weighings, re(4): done in 3 weighings.... I think =PHugo2004-07-27 10:50:56
re(4): done in 3 weighings.... I think =PVina2004-07-27 03:26:15
re(3): done in 3 weighings.... I think =PBrian Smith2004-07-26 21:53:33
re(2): done in 3 weighings.... I think =PVina2004-07-26 14:06:20
re: done in 3 weighings.... I think =PBrian Smith2004-07-26 08:11:29
done in 3 weighings.... I think =PVina2004-07-25 22:42:50
Some Thoughtsre: Why use a computer, common sense saysFederico Kereki2004-07-25 21:05:16
re: Why use a computer, common sense saysJuggler2004-07-25 17:16:45
SolutionWhy use a computer, common sense saysJuggler2004-07-25 17:04:35
But that leaves the question....Penny2004-07-25 16:27:00
SolutionAll the examplesCharlie2004-07-25 14:12:08
Four weighingsHugo2004-07-25 13:26:55
Some ThoughtsAn exampleCharlie2004-07-25 12:36:07
re: a computerized startCharlie2004-07-25 12:18:58
A non-computerized finishPenny2004-07-25 12:07:26
re: a computerized startCharlie2004-07-25 12:06:55
Hints/Tipsa computerized startCharlie2004-07-25 11:58:17
re: fewest numbers = 4Penny2004-07-25 11:15:05
Some Thoughtsfewest numbers = 4peychinhwee2004-07-25 09:55:48
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