# How many chords can be drawn for a circle with 21 points on the circle?

$\begin{array}{1 1} (21)! \\ 210 \\ (20)! \\ 42 \end{array}$

A chord can be drawn using any two points on the circle.
None of the points are collinear.
$\therefore$ No. of chords = $^{21}C_2=210$