Question

Is this correct?

consider determining how many possible phone numbers are in an area code (repeated numbers allowed)

Is this a combination, a permutation, or neither?

I think it would be a combination wouldn't it?

Since there are ten number possibilities in each of the three spaces of the area code and repeats are allowed, there are 10^3 (1000) possible permutations.

To distinguish combinations from permutations, see the following sources:

http://mathforum.org/dr.math/faq/faq.comb.perm.html
http://tutors4you.com/permutationcombinationtutorial.htm
http://en.wikipedia.org/wiki/Combinatorics
http://betterexplained.com/articles/easy-permutations-and-combinations/

I hope this helps. Thanks for asking.