Question

Tick (✓) the correct answer:
How many diagonals are there in a polygon having 12 sides?
(a) 12
(b) 24
(c) 36
(d) 54

Answer 1

(d) 54
For an n-sided polygon:
Number of diagonals = $\frac{n\left(n-3\right)}{2}$

$$\begin{gathered} \therefore n=12 \\ \Rightarrow \frac{12\left(12-3\right)}{2}=54 \end{gathered}$$