Question

If the order of selection is considered relevant, in how many ways can k objects be selected from a set of n objects?

Answer 1

hi,

You have to use a formula which is  known as of binomial coefficient which is :

k among n  is  :   C ( n /k) =   n!  / k! ( n-k)!

! = factorial

ex :   5 object among 8 is :    C ( 8/5 ) = 8 ! / 5! * ( 8-5) !

As 8! =  8*7*6*5*4*3*2*1 =  40 320

As 5! = 5*4*3*2*1 = 120  

as 3 ! = 3*2*1 = 6

then :     40 320  / 120 * 6

               40 320 / 720 = 56  

Conclusion : there is  56 way to select  5 object among 8 of them.  

ps : you can also use Pascal Triangle to do such a thing.