i need to know that which books should i prefer for iit preparation?

Dear Ms. Swati

You can go with these books for IITJEE:

Physics:
1. H.C.Verma
2. NCERT Physics
3. B.P.Bhatnagar
4. Halliday-Resnick

Chemistry:
1. NCERT Chemistry
2. I.L.Finar(Reference)
3. R.C.Mukherjee
5. J.D.Lee [Refence,selected parts]

Mathematics:
1. TMH IIT Mathematics
2. M.L.Khanna(only difficult chapter like 3D)
3. I.A.Maron
4. A.Dasgupta

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All the best.
Regards,
Askiitians Experts
Pramod Kumar
IITR Alumni