The Odd Ball
1,442.6K Views
There are twelve identical-looking balls, but one is either heavier or lighter than the other eleven. How can you determine which is the odd ball and find out whether this ball is heavier or lighter than the others using only three weighings with a balance?
Label the balls from 1 to 12 to identify them.
Weigh 1, 2, 3, 4 against 5, 6, 7, 8:
- If they balance, 9, 10, 11, 12 contain the odd ball.
Weigh 6, 7, 8 against 9, 10, 11.- If they balance, 12 is the odd ball. Weigh 12 against any other ball to discover whether it is heavy or light.
- If 9, 10, 11 are heavy, they contain an odd heavy ball. Weigh 9 against 10. If they balance, 11 is the odd heavy ball, otherwise the heavier of 9 and 10 is the odd ball.
- If 9, 10, 11 are light, we use the same procedure to reach the same conclusion for the odd light ball.
- If 5, 6, 7, 8 are heavy, either they contain an odd heavy ball or 1, 2, 3, 4 contain an odd light ball.
Weigh 1, 2, 5 against 3, 6, 10.- If they balance, the odd ball is 4 (light) or 7 or 8 (heavy). Weigh 7 against 8. If they balance 4 is light, otherwise the heavier of 7 and 8 is the odd heavy ball.
- If 3, 6, 10 are heavy, the odd ball can be 6 (heavy) or 1 or 2 (light). Weigh 1 against 2. If they balance 6 is heavy, otherwise the lighter of 1 and 2 is the odd light ball.
- If 3, 6, 10 are light, the odd ball is 3 and light or 5 and heavy. We thus weigh 3 against 10. If they balance, 5 is heavy, otherwise 3 is light.
- If 5, 6, 7, 8 are light we use a similar procedure to that in II.
Your Answer
More puzzles to try-
Distribution of Coins
Seven Robbers robbed a bank and hide the coins in a lonely place. They decide to divide the money equally ...Read More »Sides of Circle
How many sides does a circle have?Read More »Did you break it?
What is so fragile that when you say its name, you break it?Read More »What day is today
Tomorrow is neither Wednesday nor Thursday. Yesterday was not Friday or Saturday. Today is not Thursday nor Monday nor Sunday. ...Read More »For meeting her dreams riddle
A girl goes to her mother’s funeral and meets the man of her dreams but she doesn’t get his name ...Read More »Time Zones
Client Dempsey living in one of the East Coast states of the U.S. was talking to Landon Donovan, who was ...Read More »Speed of the train
A railway track runs parallel to a road until a bend brings the road to a level crossing. A cyclist ...Read More »what is written in the picture
5 sisters in a room puzzle
There are 5 sisters in a room: Ann is reading a book, Margaret is cooking, Kate is playing chess, Marie ...Read More »Five digit riddle
Can you find a five digit number which when you place a 7 at the beginning to make a new ...Read More »Who is his wife puzzle
Looking carefully at the picture can you identify his wifeRead More »Traffic Violation
There are two traffic police standing along a one-way street looking for traffic violations. They spot a taxi driver going ...Read More »What is it?
No matter how much rain comes down on it it won’t get any wetter. What is it?Read More »Stand Behind Riddle
John is asked to stand behind Jacob and Jacob is asked to stand behind John. Both of them feel confused ...Read More »Father and Son Age
When my father was 31 I was 8. Now he is twice as old as me. How old am I?Read More »Empty pocket riddle
A pants pocket is empty but still have something in it? How? What is in it?Read More »If you have me, you want to share me riddle
If you have me, you want to share me. But if you share me, you no longer have me. What ...Read More »Which is the Top View Puzzle
Find out which of the given views in the picture is the top view of the given pyramid.Read More »Bottom at the top
What has a bottom at the top?Read More »Lost without being stolen riddle
At night they come without being fetched, And by day they are lost without being stolen.Read More »
Accenture Interview PuzzlesAdobe Interview PuzzlesAge RiddleAkbar Birbal PuzzlesAlgorithm PuzzlesAlphabet riddleAmazon Interview PuzzlesAnalytical MathematicsAptitude PuzzleBank PuzzlesBetting PuzzlesBrain TeasersCalendar PuzzlesCards PuzzlesChess Board PuzzleChess PuzzlesChristmas Puzzlecipher PuzzleCivil Services PuzzleClock time puzzleCognizant Interview PuzzlesCoins PuzzleComputational PuzzleconundrumCoronavirus PuzzleCoupondunia Interview PuzzleCritical Thinking Puzzledata analyticsData Structure Interview QuestionsDecode PuzzleDetective PuzzlesDice PuzzleDictionary Riddlesdifficult riddleEasy Math puzzlesEasy puzzlesEinstein puzzleEnglish RiddleFamily Tree Puzzlefamous puzzleFill in the blanks riddlesFinding Killer RiddlesFlipkart interview puzzlesFunny RiddlesGeneral KnowledgeGeographical PuzzleGoogle Code Jam 2014Google Interview PuzzlesGRE PuzzleHard Puzzle