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March 29, 2015

March 29, 2015

Posted by **angela** on Thursday, May 13, 2010 at 8:11pm.

- math -
**Damon**, Thursday, May 13, 2010 at 8:23pmI assume 0 through 9 are allowed and repeats are possible. For example 000-0000 is allowed.

How many prefixes?

10*10*10 = 1,000

how many digits

10*10*10*10 = 10,000

so 10^3 * 10^4 = 10^7 = 10 million

I guess that is why they needed area codes.

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