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IGCSE maths paper4 question help Watch

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    Hi guys, I think I'm probably just not approaching this correctly and the mark scheme is useless so here is the question:

    The information: Polygons, their number of sides and their total number of diagonals:
    ----------------------------------------------
    Number of sides 3,4,5,6, 7 , 8
    Total number of diagonals: 0,2,5,9,14,20
    ----------------------------------------------
    The questions:
    (a) A polygon with n sides has a total of 1/pn(n - q) diagonals, where p and q are integers.
    (i) Find the values 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 with 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.

    ----------------------------------------------
    How would you approach this? I'm clueless apart from the fact you start (a)(i) by inserting 2 values from the table but I couldn't get further to find p and q. Could someone explain?

    Answers:
    a)(i) p = 2 , q = 3
    (a)(ii) 4850
    (a)(iii) 20
    (b) 31
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    Can you tell me which paper is this exactly?
    You can look it up on igcseworld.com, pastpapers.net, etc.. .
    Tell me the year, variant and question number and I will solve it in video for you
    • Thread Starter
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    It's:

    Question 10

    Paper 4 (Extended) 0580/42
    May/June 2010

    Some numbers in the bottom left:
    IB10 06_0580_42/2RP
    Cambridge IGCSE


    That's what it says on the front - thanks
    Josh
 
 
 
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