Dear Student,

Although most of the syllabus for Mathematics (311) NIOS is what you've studied till 10th.

So I'd suggest you to go through all the topics in the subject, provided in PGF form at Nios Website.

https://nios.ac.in/online-course-material/sr-secondary-courses/mathematics-(311).aspx

There are lot YouTube videos available.Also,take help from your friends and you can ask any question at this website.This would be enough to prepare you .And if you still feel like you need more préparation then,go for Crash Courses.

Best of luck.