why it takes so much time when the answer is wrong?......its so frustrating.
When you start a lesson it dowloads all the model answers so when you answer with a model answer it responds immediately. However, if you answer with a different answer it has to go back to the server to have your answer checked so there is a noticable delay.
i think it should not go to the server because it will be wrong anyway and there is a report option if there is such kind of issue. I don't know if I am right but there is a need to stop it.
I'm not much of a scripter myself, but I think it's cause in this case, the computer has to check if your answer matches any of the possible correct answers. For long sentences with many words that have synonyms, there may be hundreds of correct answers. For example the German sentence "ich spreche uber den garten mit meiner mutter" could have the following correct English translations:
I speak about the garden with my mom. I talk about the garden with my mom. I speak about the yard with my mom. I talk about the yard with my mom. I speak about the garden with my mother. I talk about the garden with my mother. I speak about the yard with my mother. I talk about the yard with my mother.
So the three main words ("spreche", "garten" and "mutter") each have two possible translations. For the entire sentence, this leads to eight correct answers. In general, the amount of possible translations will increase exponentially. For example, if you have a sentence with X words with Y translations for each word, there will be Y^X correct solutions (for the example above this is simply 2³ = 8).
Now imagine that an exercise with a long sentence has 100 correct answers. When you submit your answer, the computer would have to check if your answer matches one of those hundred. If your answer is correct, it will be finished before it needs to check all hundred, for example it could match answer 47, and it wouldn't have to check if your answer matches one of the remaining 53, which saves a lot of time. However, if your answer is wrong, the computer will have to check all 100 possible solutions before it can be sure that your answer doesn't match any of them.
I'm not sure if this is the exact reason, but I've been wondering the same thing and this is what I always assumed to be the reason.
No problem, I also just realized that the amount of correct solutions increases drastically because Duolingo allows typo's. You can leave out or add spaces, comma's, dots, etc. You can swoop in extra letters or leave out letters (as long as you don't do this too much in the same sentence), or you can write in capitals or small letters.
Despite all of these 'mistakes', the answer will still be marked correct. I think this might lead to thousands of possible answers for one exercise. That might explain the long calculation work the computer does when the answer is wrong.