Each of the physics, chemistry and mathematics subject will have 25 questions each for 100 marks from JEE 2020.

I'll guide you with some weightage..

Let's begin with Physics -

Modern Physics has a great weightage as you can expect 2-4 questions from this section. Heat and Thermodynamics, Electrostatics, Current Electricity and Optics are some other topics which are expected to have a Strong weightage.

For chemistry -

Coordination Chemistry, Periodic table will have a high enough weightage and expected questions will be 2-3 from each section. The other high weighted topics are ionic equilibrium, thermodynamics, atomic structure and chemical bonding.

Coming up to mathematics now,

Coordinate geometry, calculus and probability are some of the very high weighted topics.

To know the complete syllabus and weightage as well for JEE 2020, do refer to our website...

https://engineering.careers360.com/articles/jee-main-syllabus-weightage

Best wishes. Thank you.