A) 1140
B) 1120
C) 1120
D) 1110
Correct Answer: A
Solution :
[a] \[^{n}{{C}_{12}}{{=}^{n}}{{C}_{8}}\] \[\left[ {{\because }^{n}}{{C}_{x}}{{=}^{n}}{{C}_{y}}\Rightarrow x+y=n \right]\] \[\because 12+8=n\] \[\Rightarrow n=20.\] \[\therefore \,{{\,}^{20}}{{C}_{17}}=\frac{20}{17.3}=\frac{20\times 19\times 18}{2\times 3}=20\times 19\times 3=1140\]
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