JEE Main & Advanced Mathematics Permutations and Combinations Question Bank Self Evaluation Test - Permutations and Combinatioins

  • question_answer
    Find the number of non-negative solutions of the systems of equations: \[a+b=10,a+b+c+d=21,a+b+c+d+e+f=33,\]\[a+b+c+d+e+f+g+h=46\], and so on till \[a+b+c+d+....+x+y+z=208.\]

    A) \[^{22}{{P}_{10}}\]

    B) \[^{22}{{P}_{11}}\]

    C) \[^{22}{{P}_{13}}\]

    D) None of these  

    Correct Answer: C

    Solution :

    [c] Consider the equation \[a+b=10\] number of solutions of this equation is \[^{10+2-1}{{C}_{2-1}}=11.\] Next equation is \[a+b+c+d=21\] hence \[c+d=11\] and number of solution of this equation is 12. Similarly for third equation \[a+b+c+d+e+f=33\] or \[e+f=12\] or number of solution is 13. Similarly for last equation \[a+b+c+d+...+x+y+z=208,\] or \[y+z=22\] or number of solution is 23. Required number of ways is \[11\times 12\times 13\times ...\times 21\times 22\times 23=\frac{23!}{10!}{{=}^{23}}{{P}_{13}}\]


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