Question

How many chords can be drawn through 21 points on a circle?

Answer 1

Solution:
A chord can be drawn by joining any two points on a circle. Therefore, the number of chords that can be drawn out of 21 points is 21C2, which is given by

*21C2 = 21! / 2!19! = 212019! / 219! = 210**

Thus, the number of chords is 210.