Hello Aspirant,



Seems like you are truly motivated to get good marks and that very good. Now coming up to your question then a simple answer would be that you only know how can you get 90%. Everyone know their own true potential and you too must be knowing and if not then try to find out.You want to know how many hours you should study to get 90 then do remember one thing that from now onwards when you switch off the lights at night and hit the bed, just ask yourself that was that enough that i studied today??? if yes then have a bliss sleep and next morning give your best but if the  answer is no then switch on the lights again and study until you fall asleep by yourself.



Just remember that No gain without pain and just keep it simple





I hope this will helps.



Goodluck!