+77 On a shelf, there is space for three books, but there are five books that should be arranged. The books are numbered 1, 2, 3, 4, 5. A student has to choose three out of five books to arrange on the shelf. What is the probability that he chooses Book 3 at the first position?
+129840 To see Melody's answer....
The possible number of sets consist of the possible permutes of choosing any 3 of the 5 books = P(5,3) = 60
We want to choose the sets {3, a, b} where a,b are the possible permutes of choosing two of the other 4 books = P(4,2) = 12
So....12 / 60 = 1 / 5 .
