Question 168920
I believe you are referring to a "permutation".
.
P(n,r) = n!/(n-r)!
.
So, if you have
P(7,2) = 7!/(7-2)!
P(7,2) = 7!/5!
P(7,2) = (1*2*3*4*5*6*7)/(1*2*3*4*5)
P(7,2) = (6*7)
P(7,2) = 42