Answer:
900,000.
Step-by-step explanation:
If the number is a multiple of 10 it must end in zero.
The first digit can be any one of 0-9 except 3 - that is one of 9 digits.
All other positions (2nd to 6th) can be any one of 0 to 9 (10 digits).
So the number of possible telephone numbers is:
9*10*10*10*10*10
= 900,000.
