Question

The local seven digit telephone numbers in city A have 207 as the first three digits. How many different telephone numbers are possible in City A?

Answer 1

Given:

There are seven total digits.

The first 3 are already selected, so there is a choice for 4 digits.

There are 10 possible choices for each of the other 4 digits, so there are a total of 10×10×10×10 choices. Therefore:

`10*10*10*10=10000`

Answer: 10000