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Mathematics - Permutation & Combination Question with Solution | TestHub

MathematicsPermutation & CombinationDivision of Identical itemsMedium2 minQB

MathematicsMediumsingle choice

Number of 4 digit numbers having the sum of the digits equal to 9 is $^{11} C_{r}$ then least value of $r =$

Options:

Answer:

Solution:

$x_{1} + x_{2} + x_{3} + x_{4} = 9 x \neq = 0$ coefficient of $x^{9}$ in $(x + x^{2} + . x^{9}) (1 + x + . + x^{8})^{3}$ coefficient of $x^{8}$ in $(1 + x + . + x^{8})^{3} =^{8 + 4 - 1} C_{8} =^{11} C_{3}$

Stream:JEESubject:MathematicsTopic:Permutation & CombinationSubtopic:Division of Identical items

⏱ 2mℹ️ Source: QB

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