Multiple choice

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

  1. $301$
  2. $210$
  3. $111$
  4. $220$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A chord is formed by connecting any 2 distinct points on a circle. The number of ways to choose 2 points from 21 is given by the combination formula 21C2 = (21 * 20) / 2 = 210.

AI explanation

Two distinct points on a circle are required to draw exactly one chord. We use the combinations formula to select 2 points out of the 21 available points on the circle. Calculating 21C2 gives (21 * 20) / (2 * 1), which equals 210. Therefore, the total number of chords that can be drawn is 210.