Question

A polygon has 27 diagnols how many sides it have for class 8 method

Answer 1

Let the number of sides be n and use the formula: (1/2)n(n-3) =

number of  diagonals  = (1/2)n(n-3) = 27

Multiply both sides by 2 and then form a quadratic equation:

n2-3n-54 = 0

Solving the above quadratic equation works out as:

n = -6 or n = 9 Since the sides can't be negative, n = 9

Therefore the polygon has 9 sides.