The answer key is what you wanted, and I have seen a few, but I doubt their authenticity.  Not that the person did not put down what they knew to be true, but these exams change yearly, and no exam is made up of just one test.  Often at least two different formats of the same tests are used, for obvious reasons.  I wonder if you saw the context of the subjects that will be covered on this exam.  For example” http://gateacademy.co.in/G2/site/EnggServices2008.asp.  If you follow this link, you will see that it will take a lot more then an answer key to be successful in passing with a good result.  They do offer samples of the test questions: http://gateacademy.co.in/G2/site/Sampleyesrpapers/Microsoft%20Word%20-%20Model%20Test%20Paper-01%20_Main%20Paper_.pdf. Also this site gives you some excellent tips about doing well.