Nine points are marked on a circle. How many triangles can be drawn with all three corners among these points?

Explanation

1. 01

   No three points on a circle lie on a straight line, so any 3 points make a triangle.

2. 02

   Triangles $= {}^{9}C_{3} = \frac{9 \times 8 \times 7}{6} = 84$.