What is the correct answer? plz explain.

Remark

Let's do the problem first of all, in a way that you can understand what the answer is going to be. Start with point one. A line can be drawn to the following points from point 1.

1 to 2

1 to 3

1 to 4

1 to 5

1 to 6

1 to 7

1 to 8

Point one cannot have a line drawn to itself so you are done. There are 7 lines in all

When you move to point 2, you cannot draw a line from 2 to 1. That line is already there. So you get 2 to 3, 2 to 4, 2 to 5 ... 2 to 8 and you are done. There are 6 lines in all.

If you keep on going, you have 7 lines + 6 lines + 5 lines + 4 lines + 3 lines + 2 lines + 1 line. The total number of lines is 28.

56 is the second best answer. But the actual answer is 28.

Method 2

This method is more mathematical, but I believe harder to see. You have n points and you want to choose 2 at a time. Each point will have n - 1 lines leading away from it. In this case n = 8 and each point has 7 points leading away from it. But eventually you are going to count lines that you have already done.

8*7 = 56. But you cannot count the ones you have already done so divide by 2

8*7 /2 = 28

The general formula is n*(n - 1) /2

i pretty sure it is