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THA
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Problem details:
I think if I pretend that N is also a number from 0-9, then there would be P(10, 7) numbers without repeats, but then that's too much and I'm not sure how I can subtract the number's that N is not supposed to have. The other way I was thinking is the last 6 numbers can be chosen P(10, 6) without repeat's but then I'm not sure how I can choose the number of N. Can someone provide some help?
Given a 7 digit phone number in the form: NXX - XXXX
N = a number from 2-9
X = a number from 0-9
how many with no repeated digits?
I think if I pretend that N is also a number from 0-9, then there would be P(10, 7) numbers without repeats, but then that's too much and I'm not sure how I can subtract the number's that N is not supposed to have. The other way I was thinking is the last 6 numbers can be chosen P(10, 6) without repeat's but then I'm not sure how I can choose the number of N. Can someone provide some help?