hi,

see if you want to take nios 12th certificate you have to take atleast of 5 subjects,  the NIOS requires students to study a minimum of five and a maximum of seven subjects. There is a very wide range of subjects on offer; students, therefore, have much flexibility in selecting areas in which they are able to attempt an examination. however it would also difficult to give exam from two boards. so it would be better to  take mathematics with other subjects in your current board.