Question

If 20 points are marked on a circle, how many chords can be drawn?

Answer 1

To draw a chord we need to join two points on the circle.
There are 20 points on the circle.
∴ We can draw ²⁰C₂ chords of the circle.

= `(20!)/((20 - 2)!2!)`

= `(20!)/(18!2!)`

= `(20 xx 19xx18!)/(2xx1xx18!)`

= 190
190 chords can be drawn.