1 set
125
There are 60480 numbers.
There are 5! = 120 such numbers.
90000. With 10 digit palindromes, the last 5 digits are the same as the first 5 digits in reverse, eg 12345 54321. So it comes down to how many 5 digit numbers are there? They are the numbers "10000" to "99999", a total of 99999 - 10000 + 1 = 90000.
1 set
It is 120 if the digits cannot be repeated.
If repetition of digits isn't allowed, then no13-digit sequencescan be formed from only 5 digits.
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125
There are 7,290 different 4-digit numbers that can be formed from the digits 1-9 without repetition.
There are 625 of them - too many to list.
27 three digit numbers from the digits 3, 5, 7 including repetitions.
If the two must be different digits, then there 20 possibilities. If they can be the same one, then there are 25 possibilities.
24
500
There are 60480 numbers.