Correct Answer - Option 3 : 170
Concept:
A polygon made by joining n non-collinear points will have n sides and (nC2 - n) diagonals.
Calculation:
The polygon has n = 20 sides.
The number of diagonals will be: (20C2 - 20)
= \(\frac{20!}{2!\times18!}-20\)
= 170.
