Past simple or past continuous?

Question

1 Being students, they didn't have much money and they usually worked as waiters at weekends.

Why do we need to use the past simple?

2 While they were studying, they were working as waiters at weekends.

Is it right to use the past continuous in this case?

3 I worked from 09-00 to 18-00.

This means that I worked only from 09-00 to 18-00, right?

4 I was working from 09-00 to 18-00.

This means that I was in the process of working from 09-00 to 18-00, but I started work before 09-00 and is not a fact that I finished my work at 18-00. I am right?

Answer 1

I worked from 9:00 to 6:00 (That's the typical way of indicating time in America.) means that in the past you were definitely working from 9 to 6, but technically tells nothing about whether you were working at 5 or 7. However, it would be odd to only state part of your work time. I was working means the same thing, but it is continuous, so you can add on an event like i was working from 9 to 6 while it rained.