Instead of waiting for Divine Inspiration, try Thinking.A telephone number consists of seven digits.
The first three representing the exchange.
How many different telephone numbers are possible within the 537 exchange?
In this case repetition of numbers is possible.
So, How can I do this?
How many 4-digit combinations are possible?
Well, they range from 0000 to 9999, right?
That makes a total of . . . um . . .