There is a sentence:
Yesterday I (clean) for 3 hours.
Someone said that since we have "yesterday", it will be Past Simple and everything else doesn´t matter. However, cleaning is a process, and the way the sentence is made puts emphasis on the duration.
Which one would you say is correct:
Yesterday I cleaned for 3 hours.
Yesterday I was cleaning for 3 hours.
They are both perfectly correct. Which to use will depend on the context.
Examples
1.
A: Can I have my pay please?
B: How long did you clean for?
A: Yesterday I cleaned for 3 hours. That means you owe me £XX.YY
This is a simple measure of the time worked.
2.
A: How are you?
B: I'm tired. Yesterday I was cleaning for three hours and my back hurts.
This relates the activity that caused the discomfort.
Both versions are correct. The presence of the word "yesterday" is irrelevant.
"Clean" can denote either an accomplishment ("I cleaned the apartment in an hour") or an activity ("I cleaned the apartment for an hour"). When used with "for," it is always interpreted as an activity. For this reason, either the simple past or the past progressive can be used.
The past progressive does emphasize the duration slightly more, but the two generally have the same meaning. If you want to emphasize the duration even more, you could say: "Yesterday I spent three hours cleaning."
