4 options for the first digit, 3 options for the second digit, 2 options for the third digit. Multiply the number of options together, and you find how many 3-digit numbers you can get.
about 13
5040 numbers can be made.
456,976,000
210
Four numbers can be sorted 24 ways.
All of them.
a lot
Six - assuming 0123 does not count ... 1234 2345 3456 4567 5678 6789
5040 numbers can be made.
20 of them, if repetition is not allowed.
2
24
It is: 9C7 = 36
66
10,000
15