maths: plzz help

(a) A polygon with n sides has a total of 1/p*n(n-q) diagonals, where p and q are integers.
(i) find thhe value of p and q
(ii) find the total number of diagonals in a polygon with 100 sides
(iii) find the number of sides of a polygon which has a total of 170 diagonals
(b) a polygon with n+1 sides has 30 more diagonals than a polygon with n sides. find n

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asked by preeti
  1. 100 sides polygon have 50 diagonals

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  2. (i) I'm still working on this
    (ii) n=100 => [n(n-3)]/2 = [100(100-3)]/2 = 4850
    (iii) [n(n-3)]/2 =170 => n2-3n-340=0 <=> n = 20 and n=-17. But sides couldn't be negative => n=20 (sides)
    b) Call the total number of diagonals of n+1 sides polygon is x
    => [n(n-3)]/2=x-30 and [(n+1)(n+1-3)]/2=x
    <=> n=31

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    posted by Jensor
  3. I) p= 2
    q= 3

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    posted by Joseph
  4. Find the total number of diagonals in a polygon with 100 sides

    Formula to find the number of diagonals

    D= n(n-3) / 2. Where n is the number of sides

    D = 100(100-3)/2
    D= 100 x 97 / 2
    D = 9700/2
    D= 4850

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    posted by KK

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