You don't need higher level Mathematics to crack NID. Only basic level of Mathematics and calculations would be enough for NID. NID DAT is divided in two parts- Prelims and Mains. And the syllabus for both the exams are different. The prelims syllabus have topics like Inspiration and Creativity, Optical illusion, Innovation in Design, Design Awareness, Theme Development etc. Mains syllabus consists of Model Making, Doodling, Portfolio making, Material manipulation and mock interview etc. You can check the entire syllabus here http://design.careers360.com/articles/nid-dat-syllabus