The number of selections of four letters from the letters of the word ASSASSINATION is
72
71
66
52
As learnt in concept
Theorem of Combination -
Each of the different groups or selection which can be made by taking r things from n things is called a combination.
- wherein
Where
The Number of ways of Arrangement of objects -
The number of ways of n different objects taken all at a time
- wherein
Where 0! = 1
Case I All letters different
Case II Only 2 letters are same
Case III 2 letters repeated twice
Case IV Only 3 letters are same
Case V All letters same =1 case
Total =360+480+36+40+1=917
Option 1)
72
This is correct option
Option 2)
71
This is incorrect option
Option 3)
66
This is incorrect option
Option 4)
52
This is incorrect option