A polygon has 44 diagonals. The number of its sides isa)10b)11c)12d)13...
Solution:
Given, the polygon has 44 diagonals.
Let the number of sides of the polygon be n.
Formula:
The number of diagonals in a polygon with n sides = n(n-3)/2
Substitute the given value of diagonals in the formula,
44 = n(n-3)/2
88 = n(n-3)
n^2 - 3n - 88 = 0
Factorizing the above quadratic equation, we get
(n-11)(n+8) = 0
n = 11 or n = -8
Since n represents the number of sides of a polygon, we can eliminate the negative value of n.
Therefore, the number of sides of the polygon is 11.
Hence, option B is the correct answer.
Note:
The formula used above is derived by considering any vertex of the polygon and counting the number of diagonals that can be drawn from that vertex. We can observe that the number of diagonals drawn from a vertex is equal to the number of vertices excluding the adjacent vertices. Hence, adding up the number of diagonals from all the vertices and dividing by 2 gives the total number of diagonals in the polygon.
A polygon has 44 diagonals. The number of its sides isa)10b)11c)12d)13...
The number of diagonals for n sided polygon = [n(n-3)]/2 .therefore,=> 44 = [n(n-3)]/2 .=> n^2 - 3n - 88 = 0 .=> (n+8)(n-11) =0.=> n = -8 or 11.Neglect n = -8.Therefore,=> n = 11 .therefore, the no. of sides = 11Hence, correct answer is (B).