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  1. #1
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    Default Maths problem 00/03/2009

    My mate Groggy gave me this challenge the other day. I found it interesting. Do you want to have a go?

    In my daughter's school, there are 100 lockers, numbered 1 to 100; the summer break also happens to be exactly 100 days long; and even the cleaners are interested in numbers.

    On the first day of summer, all the lockers are unlocked. The cleaner then walks by and, for every locker, locks it if it was unlocked, and unlocks it if it was locked. (Since all the lockers were unlocked, that means he locks each one.)

    On the second day, the cleaner walks by and, for every 2nd locker starting with #2, locks it if it was unlocked, and unlocks it if it was locked. (Since all the lockers were locked after the first day, that means he unlocks each one.)

    On the third day, he walks by and, for every 3rd locker starting with #3, locks it if it was unlocked, and unlocks it if it was locked. (Now, some lockers get locked and some unlocked.)

    On the Nth day, of course, he walks by and, for every Nth locker starting with #N, locks it if it was unlocked, and unlocks it if it was locked.

    After 100 days, how many lockers are locked?
    Visit my website at www.myFineWoodWork.com

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  3. #2
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    Default

    I'll be interested to see if anyone can beat Wongo's time

  4. #3
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    Default



    BTW groggy, there is very little to do with binary. Your hint didn't really help.
    Visit my website at www.myFineWoodWork.com

  5. #4
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    Default

    If you were a lateral rather than a logical thinker, it would have been obvious

  6. #5
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    I don't agree with you.

    Visit my website at www.myFineWoodWork.com

  7. #6
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    Default

    none ---they open them all for the kids returning to school
    Cheers Fred



    The difference between light and hard is that you can sleep with the light on.
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  8. #7
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    Default

    For 100 lockers, the answer is 10.

    Hint: The answer is 10 for any number of lockers between 100 and 120.

  9. #8
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    Default

    10 is the right answer.

    What is the hint for?
    Visit my website at www.myFineWoodWork.com

  10. #9
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    Why is the bloody cleaner mucking around locking and unlocking lockers instead of cleaning? I think that's a question of much greater importance.

    Mick
    "If you need a machine today and don't buy it,

    tomorrow you will have paid for it and not have it."

    - Henry Ford 1938

  11. #10
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    Default

    Quote Originally Posted by journeyman Mick View Post
    Why is the bloody cleaner mucking around locking and unlocking lockers instead of cleaning? I think that's a question of much greater importance.

    Mick
    and not even God had to work 'til the Nth day

    Cheers
    Michael

  12. #11
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    Quote Originally Posted by Wongo View Post
    10 is the right answer.

    What is the hint for?
    Are you asking me to reveal the calculation method, or do we leave it hanging a little longer?

  13. #12
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    Mick


    Visit my website at www.myFineWoodWork.com

  14. #13
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    Quote Originally Posted by switt775 View Post
    Are you asking me to reveal the calculation method, or do we leave it hanging a little longer?
    Does your hint really lead people to the right answer? I do not think so. Probably just as bad as groggy's.
    Visit my website at www.myFineWoodWork.com

  15. #14
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    Quote Originally Posted by Wongo View Post
    Does your hint really lead people to the right answer? I do not think so. Probably just as bad as groggy's.

    So as not to spoil the fun for everyone, I'll PM you the answer.

  16. #15
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    Hey switty, you should come to the drivel forum on Fridays. Groggy gives me one of these every time. I am sure you will enjoy it as much as I do. It is fun.
    Visit my website at www.myFineWoodWork.com

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