Let f(x,y) be defined as the remainder when (x–y)! is divided by x. If x=16, what is the maximum value of y for which f(x,y)=0?  Answers
A) 5 B) 10 C) 15 D) 20 E) 25
The question is finding y such that (16-y)! is a multiple of 16. That means we need to have 2^4 in (16-y)!   6! is the smallest factorial number with 2^4 as a factor.   16-y = 6   y = 10   The answer is 10.
<result>B</result>
Let f(x,y) be defined as the remainder when (x–y)! is divided by x. If x=16, what is the maximum value of y for which f(x,y)=0?