locmsimon asked in 科學及數學數學 · 9 years ago

數學題(Combination)#3 10分

圖片參考:http://imgcld.yimg.com/8/n/HA00145646/o/7011121200...

ans: 21b=120 c=6075

請解釋以上問題,thanks

1 Answer

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  • 9 years ago
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    (21b)

    It means all committee member came from either Central Canada or Western Canada

    10C7

    = 10C3

    = 10 * 9 * 8 / (3 * 2 * 1)

    = 120

    (21c)

    all combinations = 15C7

    no representation from Eastern Canada : 10C7 = 120

    no representation from Central Canada : 10C7 = 120

    no representation from Western Canada : 10C7 = 120

    At least one representative from each region of Canada :

    15C7 - 3 * 120

    = 6435 - 360

    = 6075

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