There are 28 stations between Ernakulam and Chennai. How many second class tickets have to be printed, so that a passenger can travel from one station to any other station?  Choose one:
A) 800	B) 820	C) 850	D) 870	E) 900
The total number of stations= 30   From 30 Stations we have to choose any two stations and the direction of travel (Ernakulam to Chennai is different from Chennai to Ernakulam) in 30P2 ways.   30P2= 30*29= 
<gadget id="calculator">30*29</gadget>
<output>870</output>
870   ANSWER:870
<result>D</result>
There are 28 stations between Ernakulam and Chennai. How many second class tickets have to be printed, so that a passenger can travel from one station to any other station?