A) 2
B) 4
C) 3
D) 6
Correct Answer: C
Solution :
\[{{\,}^{15}}C{{ & }_{3r}}={{\,}^{15}}{{C}_{r+3,}}\] If \[{{\,}^{n}}{{C}_{r}}={{\,}^{n}}{{C}_{s}},\]then \[r+s=n\] Hence, \[3r+r+3=15\]or \[4r=12\] \[r=\frac{12}{4}=3\]You need to login to perform this action.
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