Simply to understand the concept of pass and fail. if you got 90% means you are 90% grasp the syllabus but10% not, in your words he is fail 10% and pass 90%. so he is also failed. it means if you got 25% out of 100 , you are not fail, you are passed 25%,remaining study 75% you have to complete. pass and fail is the conditional term, but if you think about another perspective, if you observed that its only to check yourself towards your preparation with respect to time and your determination, you have scored 25% means you only effort that level only. it means you are neither pass nor fail. only you have pass or success up yo that scored or level.