Please help!! I have a final on this stuff tomorrow.
How many different seven-digit phone numbers exist that start with the number 5 and end with an odd number?
The first digit can only be 5 ... 1 possibility. The 2nd digit can be any one of 10. For each of those . . . The 3rd digit can be any one of 10. For each of those . . . The 4th digit can be any one of 10. For each of those . . . The 5th digit can be any one of 10. For each of those . . . The 6th digit can be any one of 10. For each of those . . . The 7th digit can be any one of 5. (1, 3, 5, 7, or 9).
Total possibilities: (1 x 10 x 10 x 10 x 10 x 10 x 5) = 5 x 10⁵ = 500,000
I have no idea how many of them exist, but that's the quantity that could exist.
