Question

What can be the maximum number of points of intersection of 5 straight lines?
A) 6
B) 7
C) 10
D) 12

Answer 1

if any three lines are not concurrent and not parallel then we get maximum number of points of intersection

now 5 lines intersect remaining 4 lines but we count every line 2 times

so number of point of intersection is

5x4/2 =10

ANOTHER METHOD

WE GET ONE POINT OF INTERSECTION FOR EVERY TWO LINES

from 5 lines number of selection of 2 lines is 5C2=5x4/1×2=10