11) 10C3 - 9
Find the number of triangles that can be formed with the vertices of a polygon of 10 sides as vertices ,if
1)The triangles can not have more than one side common with the polygon
2)The triangle can not have any side common with the polygon
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5 Answers
621) 10C3 - 10 = 110
10C3 is the number of triangles that can be made out of the 10 points
10= number of triangles with 2 corresponding sides in the polygon
2) 110- 1 side
110- 10*6 = 50
where did I get 10*6 (this is not very tough. .just give it a thought!)
62
The 110 traingles that are formed include those with 1 side along the polygon. We find those by removing it.
For each side (shown in red) , there are 6 triangles formed using the green points..
there are 10 such points..
so 60 points need to be removed
