**Question:**

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:

Correct Option: , 3

**Solution:**

Total cases $=$ number of diagonals

$={ }^{20} C_{2}-20=170$