sriram
Last Activity: 7 Years ago
In general, the sum of interior angles of a rectilinear figure with ‘n’ sides = (2n – 4) Right Angles
= (2n – 4) * 90 = 180n – 360 ------ (1)
Given, a = 420; d = 330.
Assume the number of edges = n.
Then Sum of ‘n’ terms of an AP:
From (1),
180n – 360 =
360n – 720 = 84n + 33n2 – 33n
33n2 + 51n – 360n + 720 = 0
33n2 – 309n + 720 = 0
Solving the quadractic equation, n = 4.36, 5
As ‘n’ can not be in decimal point, n = 5.
