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Coombinatorics- The number of ways of choosing with parameters

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Coombinatorics- The number of ways of choosing with parameters


Different ways of coloring a $4 times 4$ game boardWhat does the “n choose multiple numbers” symbol stands for?Recurrence Relation, Discrete Math problem(Homework)Condition over CombinationsWith how many different ways can Adriana be dressed…????Counting the number of trials.Number of ways to pick balls with conditions on their colorsIn how many ways we can color $15$ eggs..In how many ways can two different colored balls be chosen?Combinatorics: Coloring a prism













2












$begingroup$


Here's the problem:




At our disposal is a collection of 10 red, 11 blue and 12 yellow fabrics. (each fabric is unique)In how many ways can we choose 4 different fabrics if we want at least one fabric of each of the three colors?




My solution was since the first fabric chosen must be red, there are 10 options for it. Then the next fabric must be blue, which has 11 options. The third fabric is yellow, with 12 options, and the last fabric can be any of the colors, provided that it has not already been chosen, so there are (9+10+11-3)= 30 ways to choose the last one, making the total number of choices 9*10*11*30.



My professor said that I needed to divide that by 2 to get the right answer, but I just don't understand why. Any help would be much appreciated!










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    2












    $begingroup$


    Here's the problem:




    At our disposal is a collection of 10 red, 11 blue and 12 yellow fabrics. (each fabric is unique)In how many ways can we choose 4 different fabrics if we want at least one fabric of each of the three colors?




    My solution was since the first fabric chosen must be red, there are 10 options for it. Then the next fabric must be blue, which has 11 options. The third fabric is yellow, with 12 options, and the last fabric can be any of the colors, provided that it has not already been chosen, so there are (9+10+11-3)= 30 ways to choose the last one, making the total number of choices 9*10*11*30.



    My professor said that I needed to divide that by 2 to get the right answer, but I just don't understand why. Any help would be much appreciated!










    share|cite|improve this question







    New contributor




    cmplxliz is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
    Check out our Code of Conduct.







    $endgroup$















      2












      2








      2





      $begingroup$


      Here's the problem:




      At our disposal is a collection of 10 red, 11 blue and 12 yellow fabrics. (each fabric is unique)In how many ways can we choose 4 different fabrics if we want at least one fabric of each of the three colors?




      My solution was since the first fabric chosen must be red, there are 10 options for it. Then the next fabric must be blue, which has 11 options. The third fabric is yellow, with 12 options, and the last fabric can be any of the colors, provided that it has not already been chosen, so there are (9+10+11-3)= 30 ways to choose the last one, making the total number of choices 9*10*11*30.



      My professor said that I needed to divide that by 2 to get the right answer, but I just don't understand why. Any help would be much appreciated!










      share|cite|improve this question







      New contributor




      cmplxliz is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.







      $endgroup$




      Here's the problem:




      At our disposal is a collection of 10 red, 11 blue and 12 yellow fabrics. (each fabric is unique)In how many ways can we choose 4 different fabrics if we want at least one fabric of each of the three colors?




      My solution was since the first fabric chosen must be red, there are 10 options for it. Then the next fabric must be blue, which has 11 options. The third fabric is yellow, with 12 options, and the last fabric can be any of the colors, provided that it has not already been chosen, so there are (9+10+11-3)= 30 ways to choose the last one, making the total number of choices 9*10*11*30.



      My professor said that I needed to divide that by 2 to get the right answer, but I just don't understand why. Any help would be much appreciated!







      combinatorics discrete-mathematics






      share|cite|improve this question







      New contributor




      cmplxliz is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.











      share|cite|improve this question







      New contributor




      cmplxliz is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.









      share|cite|improve this question




      share|cite|improve this question






      New contributor




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      asked 4 hours ago









      cmplxlizcmplxliz

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      111




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      New contributor





      cmplxliz is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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          2 Answers
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          $begingroup$

          Because under your scheme you would count, for example, both
          $$R1,B1,Y1,R2quadhbox{and}quad R2,B1,Y1,R1 .$$
          But these are actually the same choice and therefore should not be counted twice.






          share|cite|improve this answer









          $endgroup$





















            2












            $begingroup$

            The total number of ways is $binom {10} {2} binom {11} {1} binom {12} {1} + binom {10} {1} binom {11} {2} binom {12} {1} + binom {10} {1} binom {11} {1} binom {12} {2} = 19800.$






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              2 Answers
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              2 Answers
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              3












              $begingroup$

              Because under your scheme you would count, for example, both
              $$R1,B1,Y1,R2quadhbox{and}quad R2,B1,Y1,R1 .$$
              But these are actually the same choice and therefore should not be counted twice.






              share|cite|improve this answer









              $endgroup$


















                3












                $begingroup$

                Because under your scheme you would count, for example, both
                $$R1,B1,Y1,R2quadhbox{and}quad R2,B1,Y1,R1 .$$
                But these are actually the same choice and therefore should not be counted twice.






                share|cite|improve this answer









                $endgroup$
















                  3












                  3








                  3





                  $begingroup$

                  Because under your scheme you would count, for example, both
                  $$R1,B1,Y1,R2quadhbox{and}quad R2,B1,Y1,R1 .$$
                  But these are actually the same choice and therefore should not be counted twice.






                  share|cite|improve this answer









                  $endgroup$



                  Because under your scheme you would count, for example, both
                  $$R1,B1,Y1,R2quadhbox{and}quad R2,B1,Y1,R1 .$$
                  But these are actually the same choice and therefore should not be counted twice.







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered 4 hours ago









                  DavidDavid

                  69.2k667130




                  69.2k667130























                      2












                      $begingroup$

                      The total number of ways is $binom {10} {2} binom {11} {1} binom {12} {1} + binom {10} {1} binom {11} {2} binom {12} {1} + binom {10} {1} binom {11} {1} binom {12} {2} = 19800.$






                      share|cite|improve this answer









                      $endgroup$


















                        2












                        $begingroup$

                        The total number of ways is $binom {10} {2} binom {11} {1} binom {12} {1} + binom {10} {1} binom {11} {2} binom {12} {1} + binom {10} {1} binom {11} {1} binom {12} {2} = 19800.$






                        share|cite|improve this answer









                        $endgroup$
















                          2












                          2








                          2





                          $begingroup$

                          The total number of ways is $binom {10} {2} binom {11} {1} binom {12} {1} + binom {10} {1} binom {11} {2} binom {12} {1} + binom {10} {1} binom {11} {1} binom {12} {2} = 19800.$






                          share|cite|improve this answer









                          $endgroup$



                          The total number of ways is $binom {10} {2} binom {11} {1} binom {12} {1} + binom {10} {1} binom {11} {2} binom {12} {1} + binom {10} {1} binom {11} {1} binom {12} {2} = 19800.$







                          share|cite|improve this answer












                          share|cite|improve this answer



                          share|cite|improve this answer










                          answered 3 hours ago









                          Dbchatto67Dbchatto67

                          1,134118




                          1,134118






















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