There is no trend as of such. Try to score 70%+ so that you get a good gpa.
gpa is given on subject basis and not overall basis . A student who gets 4gpa in each and every subject then only he gets 4ga for that trimester exam.
A student who gets highest total from addition of all subjects is not necessary that he will get 4gpa because he might have score less than others in one particular subject.
Getting good marks requires good internal marks .