The Number of Ways to Arrange X Successes Among N $n / x!$

Multiple Choice

The number of ways to arrange x successes among n trials is equal to

A) $n / x!$
B) $\frac { n ! } { ( n - x ) ! }$
C) $n / x$
D) $n ! / x !$
E) $\frac { n ! } { x ! ( n - x ) ! }$