A) 8
B) 9
C) 10
D) 11
E) 12
Correct Answer: B
Solution :
Number of triangle\[{{=}^{n+3}}{{C}_{3}}=220\] \[\Rightarrow \] \[\frac{(n+3)!}{3!n!}=220\] \[\Rightarrow \] \[(n+1)(n+2)(n+3)=1320\] \[=12\times 10\times 11\] \[=(9+1)(9+2)(9+3)\] \[\therefore \] \[n=9\]You need to login to perform this action.
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