I would suggest you to complete your B. tech rather then doing B.Sc(maths) correspondence. The b. tech will provide you immense opportunities.

You can do B. tech in following branches:

Chemical Engineering
Civil Engineering
Mechanical Engineering
Computer Science & Engineering
Electrical Engineering
Electronics and Communications Engineering
Metallurgical and Material Science Engineering
Mining Engineering
Production Engineering
Textile Engineering

Here I am sharing the contact details of Top 10 Engineering Colleges in India,:

Indian Institute of Technology(IIT)
Hauz Khas, Delhi 011-26591770/26591791

Indian Institute of Technology(IIT)
Nankari, Kanpur 0512-2597578/ 2597678/2597385/2597178

Indian Institute of Technology(IIT)
Kharagpur 03222-255303/913222282232/913222283827

Indian Institute of Technology(IIT)
44/A, G S TRoad, Guindy, Chennai 044-22578131/914422578030/22578060

Indian Institute of Technology
Roorkee 01332-285714/ 285270/285209/285907

Birla Institute of Technology and Sciences(BITS, Pilani)
Vidya Vihar 0159-6242013/6242211

Institute of Technology, Banaras Hindu University (IT, BHU)
Varanasi 0542-6702024

Vellore Institute of Technology(VIT) Katpadi, Vellore
0416-2243100/ 2243091

Delhi Technological University
Bawana Road, Near Sector-7, Shahbad Daulatpur, Delhi-110042, delhi 011-27871018/ 27871042/27871023

Indian Institute of Technology(IIT)
Amingaon,North Guwahati 0361-2582006/2583000/09864033979