Question

Let ab, cd, ef , gh, and jk be five diameters of a cir cle with center at 0. In how many ways can three points be chosen out of a, b, c, d, e, f , g, h, j, k, and 0 so as t o form a triangle?

Answer 1

there are 10C3 ways
$\binom{10}{3}$
because the points are 10 and out of these we have to select 3 point for to have a traingle