SOLUTION: how many 7 digit phone numbers are possible if consecutive digits must be different? is the probability equation of nPr=n!/(n-r)! correct? please help

Question 1028854: how many 7 digit phone numbers are possible if consecutive digits must be different?
is the probability equation of nPr=n!/(n-r)! correct? please help
Answer by richard1234(7193) (Show Source): You can put this solution on YOUR website!
10 choices for the first digit, and each successive digit has nine possibilities (e.g. if the first digit is 5, then there are 9 choices for the second digit (0-9 except 5)).

# numbers = 10*9^6

The equation for permutations nPr has nothing to do with it.
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