Mathematics

Joanna Robinson

17 April, 07:42

US telephone numbers consist of a 3-digit area code, a 3-digit exchange, and a 4-digit station number.

1. In how many ways can you arrange the 3-digit exchange and 4-digit

station number to form a telephone number?

2. Suppose that someone randomly dials the area code in a long-distance call (in the US). The exchange and station numbers match yours. What is the probability that the number dialed is your phone number? (note: even though some area codes are not valid, such as 000, it is still possible to dial these numbers).