Sir i got 40.69 marks with gate score 421 belonging from mechanical branch and open category .please tell me that what i can do with this sc

As per your score and previous year cutoff, the colleges you get in first round are:-

• Visvesvaraya National Institute of Technology Nagpur CAD-CAM
• National Institute of Technology Raipur Machine Design
• Maulana Azad National Institute of Technology Bhopal Stress & Vibration Analysis
• National Institute of Technology Rourkela Industrial Design
• Pt. Dwarka Prasad Mishra Indian Institute of Information Technology Design & Manufacture Jabalpur Mechatronics
• Visvesvaraya National Institute of Technology Nagpur Industrial Engineering
• National Institute of Technology Uttarakhand Machine Design
• National Institute of Technology Mizoram Thermal Engineering
• National Institute of Technology Raipur Industrial Engineering & Management
• Sardar Vallabhbhai National Institute of Technology Surat CAD-CAM

To know more about your chances of getting other colleges check out the PSU/college predictor link below:

https://engineering.careers360.com/gate-college-predictor

You can try for state government universities and private universities. With this score you can get some government universities but chance of getting those universities is low.So you can first try for those universities and if you don't get those universities then you should go for private universities. Best of luck.