Arya1556
P and Q are two positive three-digit integers having the same digits but in reverse order. Which of the following CANNOT be the difference between the two integers?
(A) 198
(B) 297
(C) 495
(D) 729
(E) 891
I have a question related to the general preparation for the quant part. For instance, speaking about the example shared above. I understood it the way that within answers there are no 0 in the middle, so the last digit of the first number should be smaller than the last digit of the second number, it means that anyway we will have 9 in the middle. So the right answer is D.
But my question is about the general mindset related to all questions in GMAT. As I see everyone is using factors and maybe some other stuff, but not real calculations as it takes a while. Is it all mentioned in any study guid? I just mean that all questions seem to be able to be resolved pretty fast with applying a specific strategy without actual resolving tasks as I used to do it during school/university years. Does anyone have any suggestions?