Dear Abhishek,

According, to the exam pattern you can check below the distribution of the marks.

Class 11th

Chemistry- 56
Physics- 52
Mathematics- 60

Class 12th

Chemistry- 64Physics- 68
Mathematics- 60

So, out of 200 marks you can check according to your preparation level how much you can score. 

It is recommended that to score good marks in your exam you should refer both 11th and 12th class syllabus.

If you don't have enough time you can focus on the topics which carries more weightage in the exam.

According, to the 2017 analysis you can check the important topics for JEE Main below

Physics

Capacitance- 6.67%

Current Electricity- 10.00%

Calorimetry & Thermal Expansion- 6.67%

KTG & Thermodynamics- 6.67%

Rigid Body Dynamics- 6.67%

Work, Power & Energy- 6.67%

Modern Physics- 10.00%

Chemistry

Chemical Bonding- 6.67%

S-Block- 6.67%

Alkyl Hallide, Alcohol & Ether (Reaction Mechanism)- 13.33%

Mole Concept- 10.00%

Mathematics

Co-ordinate Geometry (3-D)- 6.67%

Application of Derivatives- 6.67%

Functions- 6.67%

Matrix & Determinants- 6.67%

Probability- 6.67%

Good Luck!!