+0  
 
-1
49
2
avatar

Seven-digit telephone numbers are not allowed to begin with  or .

I can only remember a seven-digit telephone number if the first three digits (the "prefix") are equal to the next three digits or the last three digits. For example, I can remember 389-3892 and 274-9274.

How many seven-digit telephone numbers can I remember?

 Jun 26, 2021
 #1
avatar
0

There are 8 choices for the first digit, then 10 for the second, third, and fourth, then 1 for the rest.  So there are 8*10*10*10 = 8000 possible telephone numbers.

 Jun 26, 2021
 #2
avatar+39 
+1

Your question is not complete

 Jun 26, 2021

10 Online Users