Probability that sum of three digits is the same as sum of other three digits











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How can I solve problems like this:



Let ${c_1,c_2,c_3,c_4,c_5,c_6}$ be a random sequence where $c_iin (0,1,2,3,4,5,6,7,8,9)$ What is probability that $c_1+c_2+c_3=c_4+c_5+c_6$,



$c_1$ to $c_6$ is not a number there can be all zeroes and combination like $1,1,1$ etc. is possible.



I have a problem with getting how many is combinations there are. I saw that for a specific number like $c_1+c_2+c_3=12$, it is possible to use a generating function, but I don't know how to use it when we have statement like in this problem.










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  • Are these supposed to be the digits of 6-digit natural number? Because if so then the first digit has to be non-zero.
    – Keen-ameteur
    Nov 18 at 14:55






  • 1




    Are the numbers chosen with or without replacement?
    – Ross Millikan
    Nov 18 at 14:57










  • Please edit your question to show what you have attempted and explain where you are stuck so that you receive responses that address the specific difficulties you are encountering.
    – N. F. Taussig
    Nov 18 at 15:25















up vote
1
down vote

favorite












How can I solve problems like this:



Let ${c_1,c_2,c_3,c_4,c_5,c_6}$ be a random sequence where $c_iin (0,1,2,3,4,5,6,7,8,9)$ What is probability that $c_1+c_2+c_3=c_4+c_5+c_6$,



$c_1$ to $c_6$ is not a number there can be all zeroes and combination like $1,1,1$ etc. is possible.



I have a problem with getting how many is combinations there are. I saw that for a specific number like $c_1+c_2+c_3=12$, it is possible to use a generating function, but I don't know how to use it when we have statement like in this problem.










share|cite|improve this question
























  • Are these supposed to be the digits of 6-digit natural number? Because if so then the first digit has to be non-zero.
    – Keen-ameteur
    Nov 18 at 14:55






  • 1




    Are the numbers chosen with or without replacement?
    – Ross Millikan
    Nov 18 at 14:57










  • Please edit your question to show what you have attempted and explain where you are stuck so that you receive responses that address the specific difficulties you are encountering.
    – N. F. Taussig
    Nov 18 at 15:25













up vote
1
down vote

favorite









up vote
1
down vote

favorite











How can I solve problems like this:



Let ${c_1,c_2,c_3,c_4,c_5,c_6}$ be a random sequence where $c_iin (0,1,2,3,4,5,6,7,8,9)$ What is probability that $c_1+c_2+c_3=c_4+c_5+c_6$,



$c_1$ to $c_6$ is not a number there can be all zeroes and combination like $1,1,1$ etc. is possible.



I have a problem with getting how many is combinations there are. I saw that for a specific number like $c_1+c_2+c_3=12$, it is possible to use a generating function, but I don't know how to use it when we have statement like in this problem.










share|cite|improve this question















How can I solve problems like this:



Let ${c_1,c_2,c_3,c_4,c_5,c_6}$ be a random sequence where $c_iin (0,1,2,3,4,5,6,7,8,9)$ What is probability that $c_1+c_2+c_3=c_4+c_5+c_6$,



$c_1$ to $c_6$ is not a number there can be all zeroes and combination like $1,1,1$ etc. is possible.



I have a problem with getting how many is combinations there are. I saw that for a specific number like $c_1+c_2+c_3=12$, it is possible to use a generating function, but I don't know how to use it when we have statement like in this problem.







probability combinatorics






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edited Nov 18 at 16:11









N. F. Taussig

42.8k93254




42.8k93254










asked Nov 18 at 14:51









Gokuruto

123




123












  • Are these supposed to be the digits of 6-digit natural number? Because if so then the first digit has to be non-zero.
    – Keen-ameteur
    Nov 18 at 14:55






  • 1




    Are the numbers chosen with or without replacement?
    – Ross Millikan
    Nov 18 at 14:57










  • Please edit your question to show what you have attempted and explain where you are stuck so that you receive responses that address the specific difficulties you are encountering.
    – N. F. Taussig
    Nov 18 at 15:25


















  • Are these supposed to be the digits of 6-digit natural number? Because if so then the first digit has to be non-zero.
    – Keen-ameteur
    Nov 18 at 14:55






  • 1




    Are the numbers chosen with or without replacement?
    – Ross Millikan
    Nov 18 at 14:57










  • Please edit your question to show what you have attempted and explain where you are stuck so that you receive responses that address the specific difficulties you are encountering.
    – N. F. Taussig
    Nov 18 at 15:25
















Are these supposed to be the digits of 6-digit natural number? Because if so then the first digit has to be non-zero.
– Keen-ameteur
Nov 18 at 14:55




Are these supposed to be the digits of 6-digit natural number? Because if so then the first digit has to be non-zero.
– Keen-ameteur
Nov 18 at 14:55




1




1




Are the numbers chosen with or without replacement?
– Ross Millikan
Nov 18 at 14:57




Are the numbers chosen with or without replacement?
– Ross Millikan
Nov 18 at 14:57












Please edit your question to show what you have attempted and explain where you are stuck so that you receive responses that address the specific difficulties you are encountering.
– N. F. Taussig
Nov 18 at 15:25




Please edit your question to show what you have attempted and explain where you are stuck so that you receive responses that address the specific difficulties you are encountering.
– N. F. Taussig
Nov 18 at 15:25










2 Answers
2






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up vote
2
down vote



accepted










It seems that you know how to compute $$p_k:=Pbigl[c_1+c_2+c_3=kbigr]qquad(0leq kleq27) .$$
The final result $p$ is then simply given by
$$p=sum_{k=0}^{27}p_k^2 .$$
By the way: The generating function for the number of choices of $c_1$, $c_2$, $c_3$ summing to a given $k$ is
$$left(sum_{i=0}^9 x^iright)^3=(1-x^{10})^3(1-x)^{-3}=(1-3x^{10}+3x^{20}-x^{30}bigr)sum_{j=0}^infty{2+jchoose j}x^j .$$






share|cite|improve this answer




























    up vote
    0
    down vote













    You are looking for
    $$N_{,b} (s,r,m) = text{No}text{. of solutions to};left{ begin{gathered}
    0 leqslant text{integer }x_{,j} leqslant r hfill \
    x_{,1} + x_{,2} + cdots + x_{,m} = s hfill \
    end{gathered} right.$$



    which is given by
    $$
    N_b (s,r,m)quad left| {;0 leqslant text{integers }s,m,r} right.quad =
    sumlimits_{left( {0, leqslant } right),,k,,left( { leqslant ,frac{s}{r+1}, leqslant ,m} right)}
    {left( { - 1} right)^k binom{m}{k}
    binom
    { s + m - 1 - kleft( {r + 1} right) }
    { s - kleft( {r + 1} right)} }
    $$

    as widely explained in this related post.



    Of course in this case it is $m=3$ , $r=9$ amd $0 le s le 27$.






    share|cite|improve this answer





















      Your Answer





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      2 Answers
      2






      active

      oldest

      votes








      2 Answers
      2






      active

      oldest

      votes









      active

      oldest

      votes






      active

      oldest

      votes








      up vote
      2
      down vote



      accepted










      It seems that you know how to compute $$p_k:=Pbigl[c_1+c_2+c_3=kbigr]qquad(0leq kleq27) .$$
      The final result $p$ is then simply given by
      $$p=sum_{k=0}^{27}p_k^2 .$$
      By the way: The generating function for the number of choices of $c_1$, $c_2$, $c_3$ summing to a given $k$ is
      $$left(sum_{i=0}^9 x^iright)^3=(1-x^{10})^3(1-x)^{-3}=(1-3x^{10}+3x^{20}-x^{30}bigr)sum_{j=0}^infty{2+jchoose j}x^j .$$






      share|cite|improve this answer

























        up vote
        2
        down vote



        accepted










        It seems that you know how to compute $$p_k:=Pbigl[c_1+c_2+c_3=kbigr]qquad(0leq kleq27) .$$
        The final result $p$ is then simply given by
        $$p=sum_{k=0}^{27}p_k^2 .$$
        By the way: The generating function for the number of choices of $c_1$, $c_2$, $c_3$ summing to a given $k$ is
        $$left(sum_{i=0}^9 x^iright)^3=(1-x^{10})^3(1-x)^{-3}=(1-3x^{10}+3x^{20}-x^{30}bigr)sum_{j=0}^infty{2+jchoose j}x^j .$$






        share|cite|improve this answer























          up vote
          2
          down vote



          accepted







          up vote
          2
          down vote



          accepted






          It seems that you know how to compute $$p_k:=Pbigl[c_1+c_2+c_3=kbigr]qquad(0leq kleq27) .$$
          The final result $p$ is then simply given by
          $$p=sum_{k=0}^{27}p_k^2 .$$
          By the way: The generating function for the number of choices of $c_1$, $c_2$, $c_3$ summing to a given $k$ is
          $$left(sum_{i=0}^9 x^iright)^3=(1-x^{10})^3(1-x)^{-3}=(1-3x^{10}+3x^{20}-x^{30}bigr)sum_{j=0}^infty{2+jchoose j}x^j .$$






          share|cite|improve this answer












          It seems that you know how to compute $$p_k:=Pbigl[c_1+c_2+c_3=kbigr]qquad(0leq kleq27) .$$
          The final result $p$ is then simply given by
          $$p=sum_{k=0}^{27}p_k^2 .$$
          By the way: The generating function for the number of choices of $c_1$, $c_2$, $c_3$ summing to a given $k$ is
          $$left(sum_{i=0}^9 x^iright)^3=(1-x^{10})^3(1-x)^{-3}=(1-3x^{10}+3x^{20}-x^{30}bigr)sum_{j=0}^infty{2+jchoose j}x^j .$$







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Nov 18 at 16:49









          Christian Blatter

          171k7111325




          171k7111325






















              up vote
              0
              down vote













              You are looking for
              $$N_{,b} (s,r,m) = text{No}text{. of solutions to};left{ begin{gathered}
              0 leqslant text{integer }x_{,j} leqslant r hfill \
              x_{,1} + x_{,2} + cdots + x_{,m} = s hfill \
              end{gathered} right.$$



              which is given by
              $$
              N_b (s,r,m)quad left| {;0 leqslant text{integers }s,m,r} right.quad =
              sumlimits_{left( {0, leqslant } right),,k,,left( { leqslant ,frac{s}{r+1}, leqslant ,m} right)}
              {left( { - 1} right)^k binom{m}{k}
              binom
              { s + m - 1 - kleft( {r + 1} right) }
              { s - kleft( {r + 1} right)} }
              $$

              as widely explained in this related post.



              Of course in this case it is $m=3$ , $r=9$ amd $0 le s le 27$.






              share|cite|improve this answer

























                up vote
                0
                down vote













                You are looking for
                $$N_{,b} (s,r,m) = text{No}text{. of solutions to};left{ begin{gathered}
                0 leqslant text{integer }x_{,j} leqslant r hfill \
                x_{,1} + x_{,2} + cdots + x_{,m} = s hfill \
                end{gathered} right.$$



                which is given by
                $$
                N_b (s,r,m)quad left| {;0 leqslant text{integers }s,m,r} right.quad =
                sumlimits_{left( {0, leqslant } right),,k,,left( { leqslant ,frac{s}{r+1}, leqslant ,m} right)}
                {left( { - 1} right)^k binom{m}{k}
                binom
                { s + m - 1 - kleft( {r + 1} right) }
                { s - kleft( {r + 1} right)} }
                $$

                as widely explained in this related post.



                Of course in this case it is $m=3$ , $r=9$ amd $0 le s le 27$.






                share|cite|improve this answer























                  up vote
                  0
                  down vote










                  up vote
                  0
                  down vote









                  You are looking for
                  $$N_{,b} (s,r,m) = text{No}text{. of solutions to};left{ begin{gathered}
                  0 leqslant text{integer }x_{,j} leqslant r hfill \
                  x_{,1} + x_{,2} + cdots + x_{,m} = s hfill \
                  end{gathered} right.$$



                  which is given by
                  $$
                  N_b (s,r,m)quad left| {;0 leqslant text{integers }s,m,r} right.quad =
                  sumlimits_{left( {0, leqslant } right),,k,,left( { leqslant ,frac{s}{r+1}, leqslant ,m} right)}
                  {left( { - 1} right)^k binom{m}{k}
                  binom
                  { s + m - 1 - kleft( {r + 1} right) }
                  { s - kleft( {r + 1} right)} }
                  $$

                  as widely explained in this related post.



                  Of course in this case it is $m=3$ , $r=9$ amd $0 le s le 27$.






                  share|cite|improve this answer












                  You are looking for
                  $$N_{,b} (s,r,m) = text{No}text{. of solutions to};left{ begin{gathered}
                  0 leqslant text{integer }x_{,j} leqslant r hfill \
                  x_{,1} + x_{,2} + cdots + x_{,m} = s hfill \
                  end{gathered} right.$$



                  which is given by
                  $$
                  N_b (s,r,m)quad left| {;0 leqslant text{integers }s,m,r} right.quad =
                  sumlimits_{left( {0, leqslant } right),,k,,left( { leqslant ,frac{s}{r+1}, leqslant ,m} right)}
                  {left( { - 1} right)^k binom{m}{k}
                  binom
                  { s + m - 1 - kleft( {r + 1} right) }
                  { s - kleft( {r + 1} right)} }
                  $$

                  as widely explained in this related post.



                  Of course in this case it is $m=3$ , $r=9$ amd $0 le s le 27$.







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered Nov 18 at 17:08









                  G Cab

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