I decided to allow "How old is she?" because it gets the same meaning across, but it's still not the best translation, since in Danish you'd generally use: "Hvor gammel er hun?" whenever using "How old is she?".
Which way is more commonly used in danish? "Hvor gammel er hun" or "hvad er hendes alder"??
"What is her age" sounds like very unnatural English to me, if not "how old is she" it should be "what age is she" I think.
Well, according to my American sources it is perfectly reasonable to say: "What is her age?" and thus it is chosen as the best translation because it is also the most literal translation. I have added "What age is she?" since this would also be correct. "How old is she?" is not that similar, and thus I have not added it this time around, but if you really feel that it is the same as the two others, then I'm open for suggestions.
"How old is she?" is basically equivalent in meaning and I think it should be accepted as well.
I wouldn't add 'how old is she' because wouldn't the correct Danish equivalent of that be "Hvor gammel er hende?"
I was talking with my friends (I'm American) and we do say "what is her/his age?" but almost always specifically when referring to babies/children and pets. So we would never talk about a grown woman or man and say's what's their age, but rather how old is he/she. In think, in the end, we're splitting hairs and go with what feels best. I think we all learned something from this and that's the point.
What is her age? is correct word order in English, When you start with a 'Question-word', without noun. But it is a formal phrase, not something you say among friends, that's why it sounds unusual. 'What age is she?' does not sound right. Don't add it.
You should allow "how old is she?", as this is the most common form of this expression as spoken in the UK in normal conversation. "What age are you?" etc. are also used, but mainly in formal texts.
The only time i've heard "What is her age?" or "What is your age?" is in a formal setting (i.e. Doctors office, Court official, Police officer...) "How old is she?" is informal and most common way to ask.
In French this turn of phrase is perfectly correct (especially in administrative situations, in another cases as well).
'her age' appears plural to me...? Hendes alder. Literally 'hers ages', is it not? Can someone explain why?