Find the number of marked points on the plane, if when connected pairwise by line segments, the total number of line segments formed is 15 .

Step-by-step solution

Let there be n points on the plane, then the number of line segments = n c 2 n c 2 = 15 ⇒ n ( n - 1 ) 2 = 15 ⇒ n ( n - 1 ) = 30 ⇒ n = 6