Friday, August 28, 2009

Data Management for Fun

Today, I was with a bunch of friends. When someone had to leave, this math equation popped into my head. (I know, I'm a nerd)

If there are 10 friends, and each friend has to hug everyone else, how many hugs have taken place?

I've learned to solve these types of questions in high school, but I seem to have forgotten how to now.
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9 comments:

  1. derkAugust 29, 2009 at 12:27 PM

    90 hugs? i have no data management in me, just using my limited math.

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  2. derkAugust 29, 2009 at 12:33 PM

    wait wait wait. 45 hugs. final answer.

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  3. JessicaAugust 29, 2009 at 1:01 PM

    9x10=90
    - 9x ? = ?

    I have no idea... lol

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  4. XiaohanAugust 30, 2009 at 7:50 PM

    Derrick's right. The answer is the summation of 9.
    So you'll get 9+8+7+6+5+4+3+2+1 = 45 hugs. That's only if you don't double count. If you want to double count hugs, lets say the friends are telling each other how many people they each hugged, then it'll be 9x9. The reason you can't do 9x10 is because that means you'll hug yourself...

    Whatever floats your boat i guess.

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  5. deeseaSeptember 1, 2009 at 2:02 AM

    wow xiaohan. you just had to step in and out nerd :(

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  6. JessicaSeptember 1, 2009 at 12:07 PM

    I knew xiaohan could do explain it perfectly! Yesssssss!

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  7. XiaohanSeptember 3, 2009 at 11:04 AM

    It's actually quite simple. You don't even need math to do it. If you want, you could simply visualize it and recognize the pattern it forms. Instead of thinking about people and hugging, imagine you have dots and you are connecting the dots. For each line you form, that represents one hug. If you have learned enough math, you'd also know that this is an arithmetic series, thus giving you (n^2 - n)/2

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  8. JessicaSeptember 6, 2009 at 8:38 PM

    Yeah that's the formula I used back in high school :) lol

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  9. wendySeptember 20, 2009 at 4:57 PM

    just read this,

    this nerdy xiaohan with clear explanations is hot.

    hahaha =)

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