All phone numbers consist of a three-digit area code, a three-digit exchange, and then a four-digit number. A town uses the 587 area code and the exchange 355. How many different phone numbers are possible in this town under the follow conditions?

1 Answer
Jul 31, 2016

#9000#.

Explanation:

The Area Code can be selected in only #1# way, (i.e., #587#).

The Exchange Code can be selected in #1# way, (i.e., #355#).

After these two selection, a #4# digit No. is to be selected. We note

that the First such No. can not be #0#, so, that no. can be selected in #9# ways, (i.e., any one from #1,2,3,...,9#).

The Second, Third and Fourth No. can each be selected in #10#

ways.

Therefore, total no. of ways of selection#=1xx1xx9xx10^3=9000#.