There are 8 standard classifications of blood type. An examination for prospective laboratory technicians consists of having each candidate determine the type for 3 blood samples. How many different examinations can be given of no 2 of the samples provided for the candidate have the same type.

Answer 1

8 choose 3
=8C3
=8!/((8-3)!3!)
=8*7*6/(1*2*3)
=56