1 A piece d woltwae requres a pawedit intret Hamue pansible a. if letters can be
ID: 3195770 • Letter: 1
Question
1 A piece d woltwae requres a pawedit intret Hamue pansible a. if letters can be repeated? b. if letters cannot be repeated? c. if letters can be repeated and the password must start with X? d. if letters cannot be repeated and the pass word must start with X? e. if letters can be repeated and the password must start with YZ (in that order)? f. if letters can be repeated and the password must start and end with YZ (in that order)? g if letters can be repeated and the password must start or end with YZ (in that order)?Explanation / Answer
a) letters are repeated:
= 26*26*26*...*26 (upto 8 times) = 268
b) letters are not repeated
= 26 * 25 * 24 *23 * 22 * 21 * 20 * 19 = 62,990,928,000
c) letters are repeated but first letter is fixed to be X i.e we have now 7 places and we can select out of 25 Letters .
= 1 * 26 * 26 *26 * 26 * 26 * 26 * 26 = 267
d) letters are not repeated but first letter is fixed to be X i.e we have now 7 places and we can select out of 25 Letters .
= 1 * 25 * 24 *23 * 22 * 21 * 20 * 19 = 2,422,728,000
e) letters are repeated but first two letters are fixed to be YZ in order i.e we have now 6 places and we can select out of 26 Letters .
= 1 *1* 26 * 26 *26 * 26 * 26 * 26 = 266
f) letters are repeated and first two and last two letters are fixed in order
i.e 4 placed are already fixed and we have to fill reamining 4 places
= 1*1*26*26*26*26*1*1 = 264
g) letters can be reapeated
either password start with YZ or end with YZ in order
= password start with YZ + password end with YZ
=1*1*26*26 *26 * 26 * 26 * 26 + 26 *26 * 26 * 26 * 26 * 26*1*1
= 266 + 266
=2*266
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