There are n cities. What is the number of airlines that connected 2 different cities (airline from city A to city B is different with airline from city B to city A)?	Options:  A) n(n-1)  B) n(n+1)  C) n(n-1)/2  D) n(n+1)/2  E) n2
the Q basically asks to choose two cities out of n and since the DIRECTION is important, we are looking at Permutations or combinations with Order..   nP2=nC2∗2!=n(n−1)2∗2=n(n−1)   n(n-1)NSWER:n(n-1)
<result>A</result>
There are n cities. What is the number of airlines that connected 2 different cities (airline from city A to city B is different with airline from city B to city A)?