Maths-
General
Easy
Question
In a polygon no three diagonals are concurrent. If the total number of points of intersection of diagonals interior to the polygon be 70 then the number of diagonals of the polygon is -
- 8
- 20
- 28
- None of these
The correct answer is: 20
Point of intersection of diagonals nC4 = 70
n(n–1) (n–2) (n–3) = 70 × 24 n = 8
Total no. of diagonals = nC2 – n = 8C2 – 8 = 20
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