Check out this article if you can understand the maths... marks for A/A*/Pass is not same every year and in fact, it does not mean that much for the T-score. Very low A for all 4 subjects can turn out to be less than 200...http://www.greatminds.edu.sg/index.php?option=com_content&view=article&id=89:disclose-t-score-secret&catid=59:great-minds-club&Itemid=91