Asked by Anonymous
How many 5-digit bank security Personal Identification Numbers (PIN) codes can be formed using the characters in the set {0, 2, 4, 6, 8, a, b, c, d, y } with the restrictions below.
Note: For purposes of this problem, the PIN number can be "padded" with zeros on the left. So a 0z01a is a good PIN. (IE, PIN codes can start with zeros.)
FYI: The 5-position pin above would rate as "weak" in most systems. Most of them require at least 8 characters from the digits, upper and lower case letters and special characters, and usually do not want a reused character!
Each part below is independent of the previous parts.
(a) PINs must use exactly three a's among the five characters. (with replacement)
(b) PINs begin with the letters a or d and can repeat characters. (with replacement)
Note: For purposes of this problem, the PIN number can be "padded" with zeros on the left. So a 0z01a is a good PIN. (IE, PIN codes can start with zeros.)
FYI: The 5-position pin above would rate as "weak" in most systems. Most of them require at least 8 characters from the digits, upper and lower case letters and special characters, and usually do not want a reused character!
Each part below is independent of the previous parts.
(a) PINs must use exactly three a's among the five characters. (with replacement)
(b) PINs begin with the letters a or d and can repeat characters. (with replacement)
Answers
There are no human answers yet.
There are no AI answers yet. The ability to request AI answers is coming soon!
Submit Your Answer
We prioritize human answers over AI answers.
If you are human, and you can answer this question, please submit your answer.