SOLUTION: An ATM PIN consists of four digit chosen from 0-9, and repetition of a digit is allowed. How many PINs contain at least one "7"?

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Question 843643: An ATM PIN consists of four digit chosen from 0-9, and repetition of a digit is allowed. How many PINs contain at least one "7"?
Answer by richard1234(7193) About Me  (Show Source):
You can put this solution on YOUR website!
10^4 - (#pins containing no 7's)

= 10^4 - 9^4

= 10000 - 6561

= 3439