Question

How many diagonals are there in an octagon?

• A. $8$
• B. $16$
• C. $18$
• D. $20$

Answer 1

Answer: (D)

$20$

We know that to calculate number of diagonals in a polygon we use the formula $n\times (n-3)/2$

But here $n=8$ as it is an octagon

So,

$8\times (8-3)/2=20$

There are $20$ diagonals in an octagon