If 10 points are arranged on a circle, how many lines are needed to join every point to every other point once? First solve simpler problems to determine a pattern.

You are choosing any pair from 10 choices

the number of such cases = C(10,2)
or 10!/(8!2!) = 45

To determine the number of lines needed to join every point to every other point on a circle with 10 points, we can start by solving simpler problems to identify a pattern.

Let's start with fewer points on the circle and incrementally increase the number of points to see if we notice a trend:

1. 2 points: In this case, we only need 1 line to join the two points.

2. 3 points: To join every point to every other point once, we need 3 lines.

3. 4 points: We need 6 lines to join every point once.

4. 5 points: Here, we require 10 lines.

By observing the number of lines required for each case, we can determine a pattern. It appears that the number of lines needed follows a pattern where, for n points on the circle, the number of lines is given by the formula:

(N * (N - 1)) / 2

Where N represents the number of points on the circle.

Using this formula, let's calculate the number of lines needed for 10 points:

(N * (N - 1)) / 2 = (10 * (10 - 1)) / 2 = (10 * 9) / 2 = 90 / 2 = 45

Therefore, to join every point to every other point once on a circle with 10 points, we would need 45 lines.