Using each of the 7 digits 1, 2, 3, 4, 5, 6, 7 only once, what is the difference between the smallest 4-digit number that can be made and the largest 3-digit number that can be made?

Answer 1

largest 4 digit number = 7654
smallest 3 digit number = 123

take the difference between them

Answer 2

smallest 4 digit > 1234
largest 3 digit > 765
1234 - 765
difference > 469