Assuming that leading zeros are not counted then:
The first digit can be one of {1, .. , 9} - a choice of 9.
For each of these the second can be one of the remaining 8 digits from {1, .., 9} plus the digit 0 - a choice of 9;
For each of these two choices, the third digit can be one of the 8 unchosen digits, etc.
Thus there are 9 × 9 × 8 × 7 × 6 = 27216 such numbers.
9x9x8x7x6x5 = 81x56x30 = 136080
Using the digits of 1345678, there are 210 three digit numbers in which no digit is repeated.
If the digits can be repeated, then there are (5 x 5 x 5 x 5) = 625 different four-digit numbers.If the digits can't be repeated, then there are (5 x 4 x 3 x 2) = 120 different four-digit numbers.
9
625 if numbers can have leading 0s, 500 otherwise.
What is the sum of greatest 3-digit 4-digit 5digit
9x9x8x7x6x5 = 81x56x30 = 136080
Using the digits of 1345678, there are 210 three digit numbers in which no digit is repeated.
There are 27 of them.
5040 different 4 digit numbers can be formed with the digits 123456789. This is assuming that no digits are repeated with each combination.
Any 3 out of 4 = 4. Each set can be arranged 6 ways so 24 different numbers.
It is possible to create a 3-digit number, without repeated digits so the probability is 1.
If the digits can be repeated, then there are (5 x 5 x 5 x 5) = 625 different four-digit numbers.If the digits can't be repeated, then there are (5 x 4 x 3 x 2) = 120 different four-digit numbers.
9
757
625 if numbers can have leading 0s, 500 otherwise.
5 digit telephone numbers having at least one of their digits repeated is = total possible 5 digit telephone numbers - 5 digit telephone numbers without any digit being repeated. =(10*10*10*10*10)-(10*9*8*7*6) =100000-30240 =69760