A student committee on academic integrity has 90 ways to select a president and vice president from a group of candidates. The same person cannot be both president and vice president. How many candidates are there?
Choose the most appropriate option
A) 7
B) 8
C) 9
D) 10
E) 11
Let the number of people to choose from = n   No of people to be chosen = 2   The number of ways 2 people can be chosen from n people=nC2   Now, the two people selected can be arranged in 2! ways   Hence nC2*2!=90 which gives n=10   ANSWER:10
<result>D</result>
A student committee on academic integrity has 90 ways to select a president and vice president from a group of candidates. The same person cannot be both president and vice president. How many candidates are there?