A) 100
B) 120
C) \[-120\]
D) None of these
Correct Answer: B
Solution :
We know that \[\frac{{{C}_{1}}}{{{C}_{0}}}+2\frac{{{C}_{2}}}{{{C}_{1}}}+3\frac{{{C}_{3}}}{{{C}_{2}}}+....+n.\frac{{{C}_{n}}}{{{C}_{n-1}}}=\frac{n(n+1)}{2}\] Putting n=15, then\[\frac{15\times (15+1)}{2}=120\].
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