Factorials!

 

Statisticians use factorials when calculating potential combination and permutations and using the binomial equation.  A factorial, represented by an explanation mark (!), denotes a multiplication of the sequence of descending (natural) numbers.  For example, 5! equals 5*4*3*2*1.  1! = 1.  And n! = n * (n-1)!

 

A Practice Problem!

 

Solve:  x=10!/8!

 

Solution:  So we can break down 10!  into 10*9* 8! .  We then know that 8! in the numerator cancels out the 8! in the denominator, which leaves us  10*9 in the numerator, and therefore x=90.

 

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