A student committee on academic integrity has 42 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?
Pick.
A) 7
B) 8
C) 9
D) 10
E) 11

Rationale: "xc 1 * ( x - 1 ) c 1 = 42 x ^ 2 - x - 42 = 0 ( x - 7 ( x + 6 ) = 0 x = 7 , - 6 - 6 ca n ' t possible . hence 7 should be the answer a"
Answer: A