Translation:We are looking for an apartment which is cheaper.
In meaning: yes. But as a translation which is as close as possible to the original sentence: no. The point is: of course "less expensive" more or less means the same as "cheaper"/billiger. But "less expensive" translates to weniger teuer, not to billiger.
Wohnung has a broader meaning than just 'flat'. Apartment should be accepted.
I don't think it's as simple as that. This is a quote from Oxford Dictionaries (https://en.oxforddictionaries.com/usage/that-or-which): "Note that in British English, the word which is often used interchangeably with the restrictive that:
✓ She held out the hand which was hurt."
So it seems to me that Duo's translation might very well be fine in British English.
I think in English it would depend upon the intent. These two constructs would, to me, imply different things:
a) "We are looking for an apartment which is cheaper." (restrictive clause, no comma)
b) "We are looking for an apartment, which is cheaper." (non-restrictive clause, offset by comma)
The first one means that you're looking for an apartment which is cheaper than your existing apartment, or perhaps cheaper than one you're currently viewing in an ad. A cheaper apartment is what you're looking for, and that's essential to the sentence. So for example it might come in this context:
a) "Our existing apartment is raising the rent. We are looking for an apartment which is cheaper."
The second one means you're contrasting an apartment with some other different mode. Perhaps you're comparing it to a house, or renting a hotel for a long visit. In this case the adjectival clause clarifies the situation, but it doesn't add any essential info to "apartment".
b) "We are staying for a month so a hotel is too expensive. We are looking for an apartment, which is cheaper."
Now, do most native speakers even follow this rule? Or would grasp the difference? That's open to doubt. :)
The German sentence would be the same for both, always with the comma.
(Intonation when speaking would be different but the written form is the same.)
But your English translation is wrong in this and several other exercises. "Which" and "that" are not interchangeable" and this sentence requires "that" --
I use a computer THAT is old. I use DuoLingo, WHICH is the best language software.
"We are looking for a cheaper apartment" would get round the first problem. This was rejected by duolingo, although two sentences previously it accepted "Do you have anything cheaper?" for "Habt ihr etwas, das billiger ist?
And it is still not accepted!
Although "We are looking for a cheaper apartment" and "We are looking for an apartment which is cheaper" both carry the same meaning, the former does not demonstrate and reinforce the use of relative pronouns. So, for advanced learners, who have already mastered the basic concepts of using relative pronouns, it's not so important to answer with the latter. For beginners (whether in German overall or only on the topic of relative pronouns), an effective way for die Eule to know whether they "get it" is to require the use of relative pronouns in the English answer.
Perhaps the developers could program a means to allow certain alternative answers to be acceptable for advanced learners but not beginners. This would probably require a significant increase in resources to add/mark answers in that fashion.
It's better to use the word "günstig" I think. "Billig" has the sense of something cheaper and of worse quality , whereas günstig has the sense of something more economical but still of great value.
Looking for a cheaper apartment......is correct from point of view for a translation
Wir suchen eine billigere Wohnung = We are looking for a cheaper apartment.
Wir suchen eine Wohnung, die billiger ist = We are looking for an apartment which is cheaper.
The two mean more or less the same thing but they are grammatically different; it's best to stick with the grammar the German uses (adjective versus relative clause).
Yes, but it's completely unnatural... If you get the meaning right, then it is should be correct - we're here to learn a language, not nitpick about grammatical constructs. "We're looking for a cheaper apartment" should definitely be accepted IMHO
Require the use of relative pronouns in the English answer is an effective way for die Eule to assess whether a user understands the use of relative pronouns. If this were a construct that didn't exist in one or the other language, then obviously it wouldn't be required, but the similarities between German and English permit this as a means of teaching/reinforcing the concept.
As the MODs have posted throughout this lesson's forum pages, they are rejecting any sentence that is not using a subordinate clause (i.e., "...that is...").
While this is the intent of the person speaking, to find a cheaper apartment, the point of the lesson is to teach the use of secondary sentences, so the "more straightforward" variants, like you're suggesting here, will not be accepted in this lesson, is my guess.
Hard to say without seeing a screenshot which shows the exercise type, the prompt, what you wrote, and the error message.
Was this a "type what you hear" exercise? Did you type in German or in English?
Eine wohnung is a dwelling, apartment, flat, house, etc and all of these variants should be accepted in this exercise but are not. Reported 2/23/19
There is no German word wohnung.
You are probably confusing it with Wohnung -- which usually does not refer to a house, nor to a dwelling in general, but specifically to an apartment/flat.