A) 5
B) 6
C) 4
D) 3
Correct Answer: A
Solution :
\[^{15}{{C}_{2r+2}}{{=}^{15}}{{C}_{r-2}}\] But \[^{15}{{C}_{2r+2}}={{\,}^{15}}{{C}_{15-(2r+2)}}={{\,}^{15}}{{C}_{13-2r}}\] Þ \[^{15}{{C}_{13-2r}}=\,{{\,}^{15}}{{C}_{r-2}}\Rightarrow r=5\].You need to login to perform this action.
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