How many types of tickets must be printed so that a person can choose to travel between any of the two stations?

37 Views Asked by At

There are $13$ stations between Chennai and Coimbatore. How many types of tickets must be printed so that a person can choose to travel between any of the two stations?

1

There are 1 best solutions below

0
On

This is similar to finding the diagonals of a tridecagon (13-sided polygon). The formula is $$\frac{n(n-3)}2$$

Plugging in $13$, we get $65$ different tickets.

EDIT: I forgot to consider going around the edge of the tridecagon itself, which gives us $13$ more tickets, or a total of $78$ tickets.

The above method was simply for visualization. Another way is simply to take ${13 \choose 2}$, or the ways in which you can choose two locations out of a total of thirteen locations. This will also give you $78$.