Expert: Steve Holleran - 9/8/2008

Question
How many seven-digit telephone numbers are posible if the first two digits cannot be ones or zeros?

Answer
Hi Angela,

Okay, we're assuming that after the first two, anything goes.

So, by the Fundamental Counting Principle , we have:

      8 * 8 * 10 * 10 * 10 * 10 * 10 = 64 * 10^7

                                     = 640,000,000.

Remember, this allows for repeated digits, so you could have a number
like 7 7 5 - 5 5 5 5 and so on.

Hope this is what you wanted.
Steve