1. How long did it take for him to read the book?
1-1. He finished reading the book in 5 days.
(If this is the answer to the question, #1-1 mean that it took the whold 5 days to read the book. Am I right? In that case, we can not use 'within' instead of 'in.' What about this explanation?)
2. He finished reading the book after 5 days.
(Is this ungrammatical?)
3. He finished reading the book within 5 days.
(When he finished reading the book in one day, we can use this expression, right? What about in the UK? If in the UK, 'in' doesn't mean 'within,' the meaning of 1-1 is : It took the whole 5 days for him to finish reading the book. Am I right?)
1 answer
"in five days" means it took five days. If he started on Monday, he finished the book on Friday. Your #2 doesn't make a lot of sense. After five days could mean anything more than five days. He took a whole year to read the book?