JEE Main & Advanced
JEE Main Paper (Held on 10-4-2019 Afternoon)
question_answer
Suppose that 20 pillars of the same height have been erected along the boundary of a circular stadium. If the top of each pillar has been connected by beams with the top of all its non-adjacent pillars, then the total number beams is : [JEE Main 10-4-2019 Afternoon]
A)210
B)190
C)170
D)180
Correct Answer:
C
Solution :
Total cases = number of diagonals \[{{=}^{20}}{{C}_{2}}-20=170\]