The key in this type of problems is to advance from left to right, and to use the smallest possible digit in each case. Thus, the first digit (from the left) has to be a one, since a number doesn't start with a zero; the next digit has to be a zero; etc.
0123 or 1234 - depending on whether you allow the first digit to be zero
The largest ten digit number with no repeated digits is '9876543210'.
The greatest 4-digit number with no repeated digits is... 9876
123456.
1023456789
1234567
The largest 10-digit number with no digit repeated is 9876543210 !
The largest ten digit number with no repeated digits is '9876543210'.
The largest ten digit number with no repeated digits is '9876543210'.
9,876,543,210
The greatest 4-digit number with no repeated digits is... 9876
987654
102
9876543210
98765
123456.
1023456789
1234567