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Thread: Interesting question

  1. #1
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    Default Interesting question

    Not sure if u heard or even solved this before.

    If you are given 12 balls, of which 11 of them are of the same weight whilst 1 is of different weight from the 11.

    You have a balancing beam and 3 trials using the balancing beam, remember, only 3 trials. You can try any combination.

    How to pick out the 1 ball of different weight?

  2. #2

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    If given the "different weight" ball is lighter or heavier than the rest, it'll be real easy... but in this situation, I'm stumped!

  3. #3
    ClubSNAP Idol Adam Goi's Avatar
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    Let me give it a go.

    1st attempt:

    Divide them into 6s and use the balance. The 6 that weigh lesser keep, the heavier ones, discard.

    2nd attempt:

    Divide them into 3s and use the balance. The 'lighter ones', i.e. the 3, keep and discard the 'heavier ones'.

    3rd attempt:
    Pick any two of the 3 remaining balls and use the balance. If they weigh the same, then the 3rd ball is the one. If not, the lighter one will show up.

  4. #4

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    Same as mine..but i was pondering how to carry out Step 1 and 2. It is not stated whether the one having a different weight is lighter or heavier than the rest. So there's a possibility that in the 1st attempt, the special one will be in the heavier 6 (that is if you keep the lighter 6)
    Originally posted by AdamGoi
    Let me give it a go.

    1st attempt:

    Divide them into 6s and use the balance. The 6 that weigh lesser keep, the heavier ones, discard.

    2nd attempt:

    Divide them into 3s and use the balance. The 'lighter ones', i.e. the 3, keep and discard the 'heavier ones'.

    3rd attempt:
    Pick any two of the 3 remaining balls and use the balance. If they weigh the same, then the 3rd ball is the one. If not, the lighter one will show up.

  5. #5

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    Problem is, how do you know the "different weight" ball is lighter or heavier than the rest? (step 1)

  6. #6

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    Originally posted by AdamGoi
    Let me give it a go.

    1st attempt:

    Divide them into 6s and use the balance. The 6 that weigh lesser keep, the heavier ones, discard.

    2nd attempt:

    Divide them into 3s and use the balance. The 'lighter ones', i.e. the 3, keep and discard the 'heavier ones'.

    3rd attempt:
    Pick any two of the 3 remaining balls and use the balance. If they weigh the same, then the 3rd ball is the one. If not, the lighter one will show up.
    heh, nice try. i understand. but what if the ball tat is different is heavier and not lighter than the other 11?

  7. #7

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    my answer is, no, I'll not use the balancing beam.
    I'll use electronic one.

  8. #8
    ClubSNAP Idol Adam Goi's Avatar
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    Yah hor ... I've talked too soon; never really paid attention to Fella's post!

    Let me think again ... at the meantime, next better player?

  9. #9

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    me try me try!!!

    first try take any 8 and balance 4 each. see which side is more heavy, if both is balance, then "the one ball" is in the other 4.

    second split the 4 remaining ball and split into 2 each, then select the more heavy side.

    for the last try, you are left with 2 only, so the answer is out

  10. #10

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    same logic...in your 1st and 2nd try, the "special one" is lighter or heavier?
    Originally posted by Jester
    me try me try!!!

    first try take any 8 and balance 4 each. see which side is more heavy, if both is balance, then "the one ball" is in the other 4.

    second split the 4 remaining ball and split into 2 each, then select the more heavy side.

    for the last try, you are left with 2 only, so the answer is out
    Last edited by meng; 21st May 2003 at 08:35 PM.

  11. #11
    ClubSNAP Idol Adam Goi's Avatar
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    Hm ... the more I thought of it, the more intriguing it becomes ... I'll try it on my EM1 pupils tomorrow!

  12. #12

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    good choice!
    maybe they can give a better answer??
    Originally posted by AdamGoi
    Hm ... the more I thought of it, the more intriguing it becomes ... I'll try it on my EM1 pupils tomorrow!

  13. #13

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    *sigh*

    This is how I solve all these kinds of problems:

    http://www.google.com.sg/search?q=12...oe=UTF-8&hl=en

  14. #14

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    it's amazing how google solves all our problems.. now if only it can solve the world hunger problem, SARs and other things too

  15. #15
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    Originally posted by StreetShooter
    *sigh*

    This is how I solve all these kinds of problems:

    http://www.google.com.sg/search?q=12...oe=UTF-8&hl=en
    This is good...

    Thanks for providing the answer.... Finally can feel relieved knowing this after trying to solve for two days without any result.

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