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LeAnn01Xxx

  • one year ago

A class has 20 students. If the teacher is randomly putting students in groups of 3 to complete a project, what is the probability that three students who are best friends will be together? 1/20 3/20 1/1,140

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  1. anonymous
    • one year ago
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    easy way or hard way or both?

  2. anonymous
    • one year ago
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    actually even the hard way is not that hard

  3. LeAnn01Xxx
    • one year ago
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    It doesn't matter, just a way that i'll understand it.

  4. anonymous
    • one year ago
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    ok lets compute the number of ways to choose 3 people out of a set of 20, called "20 choose 3" and written as \(\binom{20}{3}\) or \(_{20}C_3\)

  5. anonymous
    • one year ago
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    easy to do with a calculator, it is a rather large number do you know how to compute it?

  6. LeAnn01Xxx
    • one year ago
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    One sec. Let me get my calculator.

  7. anonymous
    • one year ago
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    easier to use this http://www.wolframalpha.com/input/?i=20+choose+3

  8. LeAnn01Xxx
    • one year ago
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    OKay so is it 3/20?

  9. anonymous
    • one year ago
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    oh no

  10. anonymous
    • one year ago
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    did you open the link i sent? \[_{20}C_3=1440\]

  11. anonymous
    • one year ago
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    that is the number of possible groups of 3 only one of them has all three best friends, so probability is \[\frac{1}{1440}\]

  12. LeAnn01Xxx
    • one year ago
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    Yeah I did.

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