How many different seven-digit telephone numbers are possible if no number may begin with 0?.....the answer is 9,000,000 but I'm not sure how to get that, plz explain:)

first number could be 9 different digits, but after that we can use 10 different ones each time

so
9x10x10x10x10x10x10 = 9 000 000

Ok thank you:)

To determine the number of possible seven-digit telephone numbers, we need to consider the restrictions given. We are told that no number may begin with 0.

For the first digit, we have options from 1 to 9 since 0 is not allowed. This gives us 9 possible choices.

For the remaining six digits, each digit can be any number from 0 to 9, including repetitions. So, for each of the six remaining digits, we have 10 options.

To find the total number of possible combinations, we multiply the number of choices for each digit together. Therefore, the total number of different seven-digit telephone numbers is:

9 * 10^6 = 9,000,000

This is because there are 9 options for the first digit and 10 options for each of the remaining 6 digits.

Hence, the answer is 9,000,000.

To find the number of possible telephone numbers, we need to consider the restrictions given in the question. The first digit cannot be 0, so we have 9 options for the first digit (1-9). For the remaining six digits, we have 10 options (0-9) since repetition is allowed.

To calculate the number of possible telephone numbers, we multiply the number of options for each digit together:
9 options for the first digit × 10 options for each of the remaining six digits = 9 × 10^6 = 9,000,000.

So, there are 9,000,000 different seven-digit telephone numbers possible if no number may begin with 0.