Question: Tick (✓) the correct answer:
How many diagonals are there in a polygon having 12 sides?
(a) 12
(b) 24
(c) 36
(d) 54
Solution:
(d) 54
For an n-sided polygon:
Number of diagonals $=\frac{n(n-3)}{2}$
$\therefore n=12$
$\Rightarrow \frac{12(12-3)}{2}=54$
