SOLUTION: there are 12 points a1,a2,...a12 in a plane,no 3 on the same line,no 3 on the same line.how many triangles that contain a1 as a vertex determined?

SOLUTION: there are 12 points a1,a2,...a12 in a plane,no 3 on the same line,no 3 on the same line.how many triangles that contain a1 as a vertex determined?

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Question 1014481: there are 12 points a1,a2,...a12 in a plane,no 3 on the same line,no 3 on the same line.how many triangles that contain a1 as a vertex determined?
Answer by robertb(5830) (Show Source): You can put this solution on YOUR website!
With the point a1 excluded, two points have to be selected from the remaining eleven points to form a triangle. The number of ways of doing this is C(11, 2) = 55. Therefore there are 55 different triangles formed.
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