Dear Student ,

The answer of your query depends on several factors like in which course syllabus you are talking about .. Whether this is for semester syllabus or Competitive exam syllabus .Because , the preparation strategy is different for these both cases... to prepare for board or semester exam.. you need to be prepare from  scratch i.e. your concept should be cleared about any topic you are reading from your syllabus .. if you can't cover the total syllabus , make sure that  the chapters you are covering should be well prepared and the concept should be cleared as in those exams , you may get optional exams ( Not in all board /semester exams .. it may vary)

In case of preparing for Competitive exams, you need to cover maximum topics in short time .. as in exam , your speed and time management with your analytical skill will be verified .

Hope this answer helps !