Yes, you are eligible to appear for the MHT CET for BTech even if you passed 12th with PCB and later added Maths through NIOS, meaning you can present both marksheets; most engineering colleges in Maharashtra will accept your NIOS Maths result and consider you eligible for admission.

NIOS is recognized:

The National Institute of Open Schooling (NIOS) is a recognized board, so your additional Maths marksheet will be accepted.

Check specific requirements:

While most colleges will accept your NIOS Maths, it's always best to check the specific eligibility criteria on the college website or MHT CET official notification.

MHT CET Eligibility:

To be eligible for MHT CET, you need to have passed 12th with Physics, Chemistry, and Maths (which you have now acquired through NIOS).