Permutations And Combinations


Find the number of triangles formed by 9 points lying on the circumference of a circle.


Number of points = 9
Since 9 points lie on the circumference of a circle.
∴ All the 9 points are distinct and no three of them are collinear.
Now, one and only one triangle can be drawn through 3 distinct and non-collinear points.
∴ Number of triangles formed by 9 points by taking 3 at a time
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Some More Questions From Permutations and Combinations Chapter

Determine K, so that K + 2, 4K – 6 and 3K – 2 are three consecutive terms of an A.P.