Question

How many different phone numbers are possible in the area code 503, if the first number cannot start with a 0 or 1? Do not use commas in your answer. Answer:

Answer 1

When we are asked to find the number of different phone numbers or any other type of number. we can calculate it digit by digit. For each digit we need to find the number of digits we can place there. Finally we need to multiply those numbers.

After the area code 503 we will have only 7 numbers however we have a restriction that we cannot place 0 or 1 in the first digit. Then we start with the first digit where we have 8 remaining digits to use there. For the all other places we can use any of the 10 digits. To find the different number of phone numbers we need to multiply these possibilities.

8∗10^6=8,000,000

Answer is 8000000.