Question

If someone wants to call Havana, Cuba from the United States (US) begins with US three-digit exit code 011 followed the two-digit country code for Cuba is 53, followed by the county code of Havana is 7 and finally by seven-digit local telephone numbers. But this seven-digit local telephone numbers cannot begin with 0. How many different telephone numbers are possible?

Answer 1

• 9000000 different numbers

---------------------------

The number is basically a combination in the form of:

• abcdefg, where a can't be zero but the rest of the digits have no restrictions

Hence the possible digits:

• a = 9, b,c,d,e,f,g = 10

So possible telephone number combinations:

• 9*10⁶ = 9000000