"Hawaiians like mangoes."
Translation:Makemake ka poʻe Hawaiʻi i ka manakō.
I'm wondering the same thing. For "people" I believe someone posted in a different thread about how used in the singular it can mean "the people of one country" whereas plural would mean "peoples" as in "the French, Russian, and Jamaican peoples" where the word is referring to multiple groups of humans with distinct ethnic/cultural/national/etc. backgrounds.
As for why mangoes is singular, I am not sure either. My only guess would be that ka is used for foods that we normally wouldn't eat more than one of--similar to the way that in English we would say, "I like cherries and strawberries," but not "I like watermelons and cantaloupes."
Just a guess though, maybe someone else can give us more insight.
In English, we use the plural without an article to indicate the thing in general. So when I say, "I like Mangoes" I mean in general and not any specific mangoes. Hawaiian does not have this grammatical trick available. You must always put some determiner on every noun. I get the impression that when trying to indicate the general case, the singular ka/ke is most common, but that nā can also be used. It does mean that a sentence like this sounds like, "The Hawaiian people like the mango." Note that once you think about it, that is a very odd sentence. All Hawaiians like this one specific mango? This sentence is much more likely to mean Hawaiian people in general like mangoes in general. Context can usually clarify whether a specific thing is being talked about or examples of that thing in general. If we were talking about a specific mango already, then you would be more likely to interpret such a sentence as being about that specific mango. Unfortunately, Duolingo usually lacks context, so they often accept both translations in the English - singular with the article or plural without the article.
I assume that it's because "They don't like mango" and "They don't like mangoes" means the exact sameas it's a general statement about a group of people and the type of fruit rather than a specific mango, while the dog example probably refers to a person not liking a particular dog.
I do not really see the problem with accepting ka manako to mean the entire varietal fruit. For example:
"My diet includes the cashew (nut) and the mango (fruit)."
My question is about "Hawaiians" as ka po'e Hawai'i. It should also accept kanaka Hawai'i, but it does not. This is also a collective object, similar to mango.