"Do you all want a sandwich with cheese?"
Translation:Willen jullie allemaal een boterham met kaas?
"allemaal"/"allen" should not be required for a correct answer, imho. "You all" is covered by the "jullie." If the course is going to require the "all" to be translated for emphasis, then the English prompt should also be emphatic and read "Do all of you want..."
Interesting. I suppose it depends on which part of the English speaking world you're from? At least in the Southern US they have y'all which would become All (of) y'all. But in the end it's mainly the fault of the English language for not having a distinct 2nd person plural or conjugating the verbs properly anymore so don't blame it on the Dutch ;-)
Well, "y'all" isn't considered standard/proper English, even in the US. Although, as you note, it is very common in the Southern US. But, my comment isn't about "you plural"/jullie, that's understood. My comment is about the "allemaal" being required when translating from EN. Duo should not be requiring it unless the EN is made more emphatic.
But I would say that rather than emphasizing, the "allemaal" generalizes all present to more of a singular group you and if there are any individuals that don't want to go along they better speak up... That's the fun of having different languages.
Interesting. Maybe that's something then that the course needs to teach. That's definitely a subtlety that you would not pick up reading the EN. So, back to my original comment, that Duo should not require the "allemaal" if translating from EN. But, maybe this is not a good sentence to trans from EN and should be taught from Dutch to EN instead.
Even though this way of writing it might not be standard, saying you all as one word apparently is and one would have to pronounce with extra emphasis or add an extra all to get the intended meaning.