Find the total number of selections of A + B + C + D objects where A are alike (of 1stkind), B are alike (of 2nd kind), C are alike (of 3rd kind) and D are alike (of 4th kind).
(A +1) (B + 1) (C +1) (D+1)
The total number of selections of A + B + C + D objects where A are alike (of 1st kind), B are alike (of 2nd kind), C are alike (of 3rd kind) and D are alike (of 4th kind)
Number of ways of selecting A alike objects = Selecting zero of 1st kind of objects or Selecting one of 1st kind of objects or Selecting two of 1st kind of
objects........ Selecting (A- 1) of 1st kind of objects or Selecting all A objects of 1st kind of objects
Number of ways of selecting A alike objects = (A + 1) ways
Similarly,
Number of ways of selecting B alike objects = (B + 1) ways
Number of ways of selecting C alike objects = (C + 1) ways
Number of ways of selecting D alike objects = (D + 1) ways
Total number of selections of A + B + C + D objects
= (A +1) (B + 1)(C +1) (D+1)