"This car is only four feet long."
Translation:Níl an carr seo ach ceithre throigh ar fad.
I said "Níl an carr ach ceithre troithe ar a fhad." Admittedly I omitted the 'seo' but it also corrected the other parts of the sentence which differed from the above answer. However, NÓD has "It is six feet long, tá sé sé troithe ar a fhad." (http://www.teanglann.ie/en/eid/feet_long).
It's a dialect difference - ar fad is the "standard" way of saying "long/in length" (though it is far more commonly used to mean "complete(ly)" or "total(ly)") , the current speaker says ar fhad, and ar a fhad is just a variation (I think it probably means "it is six feet in it's length").
It might have accepted ar a fhad if you hadn't left out the seo, but that probably depends on whether anyone else reported it as an alternative.
I got this right only because it was multiple choice, otherwise I would have never know to start it with "Nil" . Is this one the same as those sentences we had that were "You are but a boy"...I haven't had one of those sentences in months and can't remember if they started with "Nil" or not.
This is basically what happens whenever there is an "only" in the sentence. Irish doesn't have a word for this, so "X does only Y" is expressed as literally "X does not [do anything] but Y"*.
GnaG calls this a semi-negative clause, in case you want to read up on it: http://nualeargais.ie/gnag/satz2.htm#leathdhiultach
Yes, it is really wrong to start this sentence with Níl ach an carr seo. The "only" in this sentence is qualifying ceithre troithe, not an carr seo.
If you think other sentences support your approach, please quote the actual sentences that you are referring to so that the differences can be printed out.
I found a couple of sentences with differences in it. But indeed I think it depends on where the "only" is referring to. Though I found also two sentences that are in English almost the same, but that differ in Irish to where the "ach" is placed in the sentence. Can you please tell me why it is different? You are only boys = Níl ionaibh ach buachaillí. She is only a student = Níl ach dalta inti.
The Níl ach dalta inti exercise is wrong. Indeed, the English to Irish exercise "She is only a student" gives Níl inti ach dalta as the translation.
The other exercises using this construction are more consistent:
Níl ionainn ach buachaillí - "We are only boys"
Níl ionainn ach cailíní - "We are only girls"
Níl iontu ach béir - "They are only bears"
Níl ionam ach bean - "I am but a woman"
Níl ionaibh ach cailíní - "You are only girls"
Níl ionaibh ach buachaillí - "You are only boys"
Níl iontu ach dlíodóirí - "They are only lawyers"
Níl ionat ach innealtóir - "You are but an engineer"
Níl ionam ach fear - "I am only a man"
Níl ann ach luch - "It is only a mouse"