Unit 1 - Matrices Determinants. Since perimeter of the triangle 30 cm. Chapter 6 - Introduction to Euclids Geometry.
Chapter 7 - Linear Equations in two variables.
While C and r are variable. NCERT Solutions for Class 9 Maths Chapter 2. Check CBSE Class 9 Maths topics deleted from syllabus for academic session 2020-21. If dont want to download use it online.