i am not able to frame a question,here is the situation in you family your father is doubting your knowledge and he is asking you very simple questions and so i want to reply him by saying why would i not know such a simple thing.it is very easy.so is this sentence" why would i not know" is grammatically correct? i want to understand the grammar behind this.this is the only question i want to answer.i have already tried but not able to portray it.