Translation:This money is not going to last the whole month.
Here in Pennsylvania in the US we would say something more like "This money will not last all month." The phrase is trying to say that there is not enough money to last ,or be sufficient to cover all of the expenses that will be incurred, that month. So I used, "This money will not last all month." and got it wrong, but I still feel it is a better translation than "This money is not going to do for the whole month."
[Note: the model answer to the exercise has been changed and this comment applies to the version quoted by NaterStWilly at the top of the page.]
Without considering whether it is a good translation, I can't see anything wrong with the English sentence. I'm not sure why you are doubtful; is it because you don't like "do" here? If that's the case then see item 2 in the dictionary entry here: http://www.collinsdictionary.com/dictionary/english/do
[Added later] It may make you feel happier with the current answer to see that this American dictionary: http://www.merriam-webster.com/dictionary/do also gives one meaning of "do" as "to be adequate or sufficient" so what the answer is really saying is "This money is not going to be sufficient for the whole month".
I would be happy with "do", but was corrected to "make", which is less known to me, at least. (I entered 'reach', which I agree wasn't the best choice, but wotds as "suffice" should be accepted, at least.) I was also corrected for entering "THESE money", so I guess it was only one note/coin... :-)
"Dar" does not mean "to do". The two words are equivalent only in the very specific sense of being sufficient to meet some need. We might say "This will not do" or in Portuguese "Isto não vai dar". They day the same thing but are both idiomatic expressions. We get to those expressions by different means. The English seems clear to native speakers - this will not do what I need to get done. The Portuguese phrase says that it will not give me ("dar") what I need to achieve my objectives. The different thought processes in English and Portuguese take us to the same place We use "dar" the same way in Spanish.
Yes, "dar" is used in lots of idiomatic expressions in Brazilian Portuguese where literal translation hardly ever works. Here's a very short list: http://www.netplaces.com/brazilian-portuguese/imperative-and-subjunctive-constructions/expression-with-the-verb-dar.htm.
"This money will not be enough for the entire month."
Was accepted on 8/28/2014.
I think this is a sentence that shouldn't be translated literally. I got the general idea of the sentence and used my Spanish. Then translated the whole sentence into the best English equivalent.