Question

A seven digit telephone number is of the form ABC-DEFG. In one particular state, the digit 'A' can be any digit except 0 and 1. The digits B and C can be any digit for 2-9. The digits D,E,F, and G can be any digit 0-9 except they can't all be the same. How many seven digit phone numbers are possible with these restrictions?

Answer 1

8 possibliess for A
8 for B
10 for D
9 for E since you used one for D
8 for F because you used two for E and D
7 for G becase y ou used three for E, F and D

so

8*8*10*9*8*7=322560 different phone numbers