Assuming leading zeros are not permitted, then:
If repeats are not allowed there are 30 possible numbers.
If repeats are allowed there are 60 possible numbers.
There are 600 of them.
5040 numbers can be made.
24 different numbers.
27
24 of them.
48 of them if digits may not be repeated. 100 if they can.
There are 600 of them.
There are 60480 numbers.
There are 4*4*3*2*1 = 96 such numbers.
125
ten factorial = 10! = 3,628,800
5040 numbers can be made.
24 different numbers.
27
6, if you don't repeat any numbers.
24 of them.
1