Question

Show that the total number of different combination of letters which can be made from the letters of the word MISSISSIPPI is 149.

Answer 1

There are $4I,4S,2P,1M$.

It is not given how many alphabets are to be taken. Hence we are at liberty to choose any number of alphabet and hence by, the number of selection is $(4+1)(4+1)(2+1)(1+1)-1$ (This $-1$) is corresponding to the situation when all are left out.
$\therefore \mathrm{5.5.3.2}-1=150-1=149$.