6.Permutation and Combination
easy

જો $^{15}{C_{3r}}{ = ^{15}}{C_{r + 3}}$ ,તો $r$ ની કિંમત મેળવો.   

A

$3$

B

$4$

C

$5$

D

$8$

(IIT-1967)

Solution

(a) $^{15}{C_{3r}}{ = ^{15}}{C_{r + 3}}{ \Rightarrow ^{15}}{C_{15 – 3r}}{ = ^{15}}{C_{r + 3}}$

$ \Rightarrow 15 – 3r = r + 3 $

$\Rightarrow r = 3$.

Standard 11
Mathematics

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