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roma 發問於 科學及數學數學 · 4 年前

Probability question?

A gumball machine has six red gumballs, four blue gumballs, and three yellow gumballs. If you buy three gumballs, what is the probability that you get 1 red and 2 blue?

Please provide explanation Thanks

2 個解答

  • 4 年前

    There are total of 13 balls, and you choose 3. So the numerator will be 3C13

    And the fraction will list: 1C6 (red) * 2C4 (blue)

    Count it: [(6!/5!)*(4!/2!2!)] / (13!/3!10!) = 18/143

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  • 4 年前

    Total number of groups of 3 gum balls: 13C3=286

    Total number of 1 red and 2 blue:4C2x6C1=6x6=36

    Probability: 36/286=18/143

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