the circle to the right has 21 points. All possible line segments have been drawn. How many line segments are there?
Another way to ask the question,
"in how many ways can I choose any 2 of the 21 points" ?
C(21,2) = 210
To find the number of line segments that can be formed with a given number of points, you can use the formula nC2, where n represents the number of points.
In this case, there are 21 points, so substituting n = 21 into the formula, we get:
21C2 = (21!)/(2!(21-2)!) = (21!)/(2!19!) = (21 × 20)/(2 × 1) = 21 × 10 = 210
Therefore, there are 210 line segments that can be formed using 21 points.