Question

"In" can also mean no longer than a particular period of time:

1. Can you finish the job in two weeks?

2. Can you finish the job within two weeks?
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The definition is from a dictionary. In this case are both the same?

3. We finished the whole project in a week.

4. We finished the whole project within a week.
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Does #3 mean the following?
3-1. It took a week for us to finish the project.
Or does #3 mean #4?

Answer 1

1 and 2 mean the same thing.

3 and 3-1 are pretty close in meaning.
4 is very close; it means it took no longer than a week to finish the project.