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# IGCSE maths paper4 question help watch

1. 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.

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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?

a)(i) p = 2 , q = 3
(a)(ii) 4850
(a)(iii) 20
(b) 31
2. 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
3. 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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