@LaKapsule44 I presume you got the audio exercise. In that case there is a difference in pronunciation between "gentil" and "gentille". "Gentil" (gen-TEE). "Gentille" (gen-TEE-ya). From the audio exercise, only the masculine form will be accepted. Unfortunately, the female audio is not correct. I have disabled the audio exercise.
Me too - and I don't think it an odd sentence at all. I wish I knew how to express the two ideas in french as they are obviously very different concepts.
BUT savoir can indeed mean to know or to know how e.g. il sait nager is he knows how to swim. It can be used when a skill is required, so I'm not sure about d'être gentil - I gues it is a kind of skill : )
When we say I knew to be nice, there is a sort of had to/should/needed to be understood. I knew (I needed) to be nice
So perhaps when the french want to say I knew to be nice,with this meaning, they might use il falloir or a derivative in the sentence somewhere.
Hopefully a french native will let us know fro sure.
As vcamp89 said, whenever "savoir" is used before an infinitive, it means "to know how to." For example:
Je sais jouer au hockey. = I know how to play hockey.
Elle savait cuisiner. = She used to know how to cook.
I cannot answer the question of how to translate "know to do something" since I'm wondering the same thing myself. Hopefully a native speaker can help here.
Before I put in my answer I thought there must be a difference and I didn't want to lose a heart so I put both "gentil" and "gentille" into google translate and replayed them over and over. I got the impression "gentille" was slightly more stressed. I replayed the duolingo audio a couple of times, and thought "yep" it sounds slightly stressed, answer is "gentille". Incorrect.
Moral of this story: Duolingo audio is atrocious.
This audio seems incorrect anyway on this page : I hear "gentille" even though it's written "gentil". And I'm French, so it's not coming from my listening skills.
This audio is correct :
This one may be a hard one for foreigners, because "gentil" and "gentille" are pretty similar as far as the pronunciation is concerned.
The end of "gentil" is pronounced like the end of "petit". The end of "gentille" is pronounced like the end of "fille".
Here is a link with both words so you can get used to the difference :
"J'étais gentil." (J'étais gentil avec lui quand je le voyais/rencontrais.)
The "X used to Y" form is almost always translated with "Imparfait" in French. However, "Imparfait" can't always be translated with the "X used to Y" form. For example: "Je mangeais quand il a frappé à la porte." = "I was eating when he knocked at the door."
I was going to leave a comment on an earlier statement 'Out, il savait' which I translated as 'Yes, he knew how' for which I received an incorrect message. Here savais is 'knew how' ...to know how is what I understood as the difference between savoir and connaitre. Did I miss something?
If this was a "translate the English to French" exercise then you're right, and you should just report it as "my answer should be accepted." If it was a listening exercise, then there is actually a slight different in pronunciation between "gentil" and "gentille" as discussed in this thread.