Hello,,

I think if you have a time you should complete all chapters in very proper manner....you have to give all the chapters equally importance but there are few chapters which are too short or too easy to cover in one shot...

First of all you have to decide which are the chapters that  you know very well,and that chapters are completed in one shot at the exam time because you know that chapter in very well manner...

You should complete all chapters with one shot at the last time of exam..

Units and dimensions, kinematics, gravitation,em waves are some chapters of physics which are covered in one shot..

Redox reaction, surface chemistry, chemistry in everyday life, environmental chemistry are some chapters of chemistry to study in one shot ..

And I think there is no chapter in maths which are completed in one shot you have to practice well..

All the best, thanks