"Children have a thousand questions."
Translation:I ragazzi hanno mille domande.
According to some online discussions and dictionaries, when talking about thousands in general terms - meaning a lot, or approximately one thousand - you use "un migliaio". For several thousand you use "migliaia".
"mille" means one thousand, as in exact number (literally that amount). The indefinite article (un) is not included. Plural is "mila" (originally milla).
"un megliaio" means about one thousand in a general, or exaggerated sense. "a migliaia" means "by the thousands".
"un migliaio di persone" - a thousand people (more or less). "due migliaia di persone" - about two thousand people.
Similarly, for hundreds, "cento" is the number one hundred (also without the indefinite article). Plural form "centos". While "un centinaio" means about a hundred of something. "centinaia" means hundreds of something.
"cintinaia di migliaia di persone" - hundreds of thousands of people.
In contrast, you do need the indefinite article with one million "un milione", a billion "un miliardo" (a 'small' billion, or milliard, a thousand million), and with "un bilione" (a 'large' billion, one million million, nowadays called a trillion). This may be because these words originally come from French, while cento and mille are from Latin.
Because Italian is a sexist language - males have precedence over females. So if there is one or more boys, its male. if there is one or more, but only girls, its female. BUT if there is at least one boy, regardless of the presence of one or more girls, then the male form is used.
Usually Duolingo asks for a literal translation - so, if the article isn't in the sentence that has to be translated,it shouldn't be in the translation either. In this case, there was no article for "children", but it was wrong to exclude it in the translation. Shouldn't there be some consistency?