i m 12th class student, my exams will be startedat 4march. how to manage my time for mainly three subjects PCM

Equal times should be given to all subjects.

Other subject are also important so give time them also.

don't make rutine hour wise but chapter wise this will make your syllabus finish before exam

because hour wise study makes problem in understanding facts. Some topic require more time than other.

So, chapter wise study is best way to complete syllabus.