The first digit can be any one of the 9. For each of these . . .
The second digit can be any one of the 8 not already used. For each of these . . .
The third digit can be any one of the 7 not already used.
Total number of possibilities = (9 x 8 x 7) = 504
To form a five-digit number using the digits 1, 2, 3, 4, and 5, each digit must be used exactly once. Since there are 5 unique digits, the total number of different five-digit numbers that can be formed is given by the factorial of the number of digits, which is 5! = 120. Therefore, 120 different five-digit numbers can be formed using the digits 12345.
500
180 of them.
It is 120 if the digits cannot be repeated.
There are 34 = 81 numbers.
5040 different 4 digit numbers can be formed with the digits 123456789. This is assuming that no digits are repeated with each combination.
10,000
36
27 three digit numbers from the digits 3, 5, 7 including repetitions.
To form a five-digit number using the digits 1, 2, 3, 4, and 5, each digit must be used exactly once. Since there are 5 unique digits, the total number of different five-digit numbers that can be formed is given by the factorial of the number of digits, which is 5! = 120. Therefore, 120 different five-digit numbers can be formed using the digits 12345.
500
24
840
There are 60480 numbers.
180 of them.
There are 3024 of them.
If the digits can be used more than once, then 900. If not, then 648.