Number of points=21

⇒n=21

A chord connects circle at two points.

⇒r=2

⇒Number of chords from 21 points= ⁿC_r

⇒ ⁿC_r= ²¹C₂

⇒²¹C₂=

⇒²¹C₂=

⇒²¹C₂=

⇒²¹C₂=

⇒²¹C₂=210 chords.

Ans: 210 chords can be drawn through 21 points on a circle.