SOLUTION: What is the probability of a seven-digit (7) phone number containing the number seven (7)?

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Question 181936This question is from textbook
: What is the probability of a seven-digit (7) phone number containing the number seven (7)? This question is from textbook

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
When you want the probability of a OR b OR c ...etc, you musrt
add the probabilities of each event occurring separately
The 1st digit can be 1-9 (0 is not allowed)
The probability of it being a 7 is 1%2F9
The rest of the digits can be 0-9, so their probability is 1%2F10
The proibability of 1 number being a 7 is then:
%281%2F9%29+%2B+6%2A%281%2F10%29
%281%2F9%29+%2B+6%2A%281%2F10%29+=+10%2F90+%2B+54%2F90
10%2F90+%2B+54%2F90+=+64%2F90
64%2F90+=+32%2F45 answer