How many different 5-digit positive integers can be formed using the digits 1, 2, 3, 4, 5, 6, and 7 if none of the digits can occur more than once in the integer?

Question

Why do you have to use permutation for this question and not combination? I don't understand why the order would matter

Answer 1

Since the order of the digits makes a difference, i.e., 123 is different from 321:

(7)(6)(5)(4)(3) = ?