CAT Quantitative Ability Questions | CAT Permutation, Combination and Probability questions
Comprehension
Directions for questions: Read the information given below and answer the questions that follow :
Each of the 11 letters A, H, I, M, O, T, U, V, W, X and Z appears same when looked at in a mirror. They are called symmetric letters.Other letters in the alphabet are asymmetric letters.
CAT/2002
Question . 36
How many four-letter computer passwords can be formed using only the symmetric letters (no repetition allowed)?
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Explanatory Answer
Method of solving this CAT Quantitative Ability Question from Permutation, Combination and Probability question
(a) Four letter passwords have four places of which
1st place can be filled in 11 ways
2nd place can be filled in 10 ways
3rd place can be filled in 9 ways
4th place can be filled in 8 ways
Total passwords formed = 11× 10 × 9 × 8 = 7920