Translation:It took two weeks.
間 literally means a time period.
But note not all time phrase is formed this way.
so it is... optional right? like a more literal version, but you can leave out the 間 and it would still be pretty much identical... right?
In my understanding, no. You must say also 間 to indicate a period.
What of the previous lessons in this set then? We built lots of sentences like this, without the 間. Just trying to understand Duo's logic.
To clarify this I brought it to HiNative. One of the best answer might have proved me wrong.
It said that the use here (as an adverb I reckon) should not have the character 間. So these are correct:
Nevertheless for week it has been a habit to say with 間, so usually
albeit less common, should not be considered as wrong.
It also said that misuse such as 三年間かかります is not rare in Japan. The provider thought it may be due to confusion with the form in 三年間でかかる(費用など)/(expense etc.) incurred over a period of 3 years.
Could you please quote an example?
I think it is concerning an action occurring at a certain time vs over a certain period.
@Keith_APP "十ヶ月かかります。" is an example of a Duolingo sentence that didn't use 間 to describe something occuring over a certain period.