The last part of a telephone number has four digits, e.g. 7814 1487 2103 2772

The last part of the telephone number can start with any digit apart from zero. The other three digits can be any number. How many four digit numbers are there?

9*10*10*10

Each number has ten possible values, 0-9, and you find the possible number of combinations by multiplying them together. So with 2 numbers it would be 10 x 10 = 100 possibles. Then x another 10 for three numbers = 1000. For the final number, if you can't have zero it's only x 9 this time, so the total would be 9000 possible numbers.

To find the number of four-digit numbers, we need to consider the possible values for each digit.

For the last digit, it can start with any digit apart from zero, so we have 9 choices (1, 2, 3, 4, 5, 6, 7, 8, 9).

For the remaining three digits (excluding the last digit), they can be any number, so we have 10 choices for each digit (0, 1, 2, 3, 4, 5, 6, 7, 8, 9).

Since each digit can be chosen independently of the others, we can apply the multiplication principle.

The total number of four-digit numbers is calculated as follows:

Number of choices for the last digit * Number of choices for the first digit * Number of choices for the second digit * Number of choices for the third digit

Therefore, the total number of four-digit numbers is:

9 * 10 * 10 * 10 = 9,000

So, there are 9,000 four-digit numbers possible.

Thank you, sorry to be slow but, is that 9,101,010? Can't believe it is this simple!