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6.Permutation and Combination
easy
यदि $^{43}{C_{r - 6}} = {\,^{43}}{C_{3r + 1}},$ तब $r$ का मान होगा
A
$12$
B
$8$
C
$6$
D
$10$
Solution
दिया है, $^{43}{C_{r – 6}}\, = {\,^{43}}{C_{3r + 1}}$
$\Rightarrow$ $r – 6 = 3r + 1$ या $r – 6 + 3r + 1 = 43$
$ \Rightarrow$ $r = – \frac{7}{2}$ (असंभव) या $r = 12$. अत: $r = 12$.
Standard 11
Mathematics
