abhishekmishra87
How many 3 letter (not necessarily distinct) words can be formed using the letters from the word TWIST ?
A. 33
B. 54
C. 45
D. 60
E. None of the above
Let's consider two cases:
1) Only one T is usedIn this case the total possibilities are \(4! = 24\) as we need to select \(3\) letters and we can select any one out of the \(4\)
(T, W, I, S) for the first one, any one out of the remaining \(3\) for the second and any one of the remaining \(2\) for the last one. The sample space is reduced to \(4\) as the two
T's are indistinguishable.
This could also have been done as \(4P3 = \frac{4!}{{(4-3)!}} = 24\) (Permutation because the order matters)
2) Two T's are usedIn this case we have to select just one letter out of the remaining \(3\)
(W, I, S) which can be arranges in 3 places.
So, the total possibilities are \(3 * 3 = 9\)
Total possibilities \(24 + 9 = 33\)
So, the answer is A.
Hope that helps.