Hi Dear,

Yes, you are allowed to use Casio FX 991 MS calculator while appearing for AKTU exam. AKTU allows students to use non programmable calculators in the exam. You can read complete guidelines and list of calculators allowed by AKTU from the notification link below:

https://erp.aktu.ac.in/Attachments/Circular/103883jsoc2px.pdf

Hope this helps.. good Luck