.
(i) Find how many different numbers can be formed using 4 of the digits 1, 2, 3, 4, 5, 6 and 7 if no digit is repeated.
(iii) odd and less than 3000
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
(i) Any of 7 digits in the first position (first counting from the left, which is "thousands" digit);
Any of 6 remaining g digits in the next position;
Any of 5 remaining g digits in the next position;
Any of 4 remaining g digits in the next position.
In all, 7*6*5*4 = 840 numbers.
(ii) It is not clear to me if repeating is allowed in this case.