There are 10 stations on a railway line. The number of different journey tickets that are required by the authorities, is

There are 10 station on railway line.
So, the number of different journey tickets between two station from given 10 stations from one side = ¹⁰C₂ = 10 x 9/2 = 45.
Similarly, number of different journey tickets from other side = 45
∴ Total number of tickets to be generated by authorities. = 45 + 45 = 90