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प्रश्न
English alphabet has 11 symmetric letters that appear same when looked at in a mirror. These letters are A, H, I, M, O, T, U, V, W, X and Y. How many symmetric three letters passwords can be formed using these letters?
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उत्तर
Number of 3 Letter passwords
= 11P3
= 11 × 10 × 9
= 990
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