Question 97754
How many quadrilaterals can be found from joining the vertices of a heptagon? Can you please provide me with a formula that will work for all polygons? 
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Quadrilaterals have four vertices.
A heptagon has seven vertices.
The number of ways you can select four from the seven is 7C4 = 7!/(7-4)!4!
= 35
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If a n-gon has n vertices you can form nC4 quadrilaterals.
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Cheers,
Stan H.