Let us discuss CBSE Sample Paper 201718 of Mathematics Class 12
There are 4 sections
Section  How many marks?  Number of Questions  Total Marks 
Section A  1 marks each  4  1 × 4 = 4 
Section B  2 marks each  8  2 × 8 = 16 
Section C  4 marks each  11  4 × 11 = 44 
Section D  6 marks each  6  6 × 6 = 36 
Total  100 
Marks per Chapter
According to CBSE Syllabus , the marks per unit is like this
Unit  Topic  Chapters of NCERT  Marks 
I.  Relations and Functions  Chapter 1, 2  10 
II.  Algebra  Chapter 3, 4  13 
III.  Calculus  Chapter 5, 6, 7, 8, 9  44 
IV.  Vectors and 3D Geometry  Chapter 10, 11  17 
V.  Linear Programming  Chapter 12  6 
VI.  Probability  Chapter 13  10 
Total  100 
In this sample paper, lets see how many questions of which chapter are asked
Chapter  1 Mark Questions  2 Mark Questions  4 Mark Questions  6 Mark Questions  Total Marks 
Chapter 1  2  1  8  
Chapter 2  2  4  
Chapter 3  1  6  
Chapter 4  1  1  1  7  
Chapter 5  1  4  
Chapter 6  1  2  10  
Chapter 7  1  1  1  12  
Chapter 8  1  6  
Chapter 9  1  2  10  
Chapter 10  1  1  1  7  
Chapter 11  1  1  10  
Chapter 12  1  6  
Chapter 13  1  2  10  
Total  100 
Points to be noted about marking

1 Question of 6 marks will come of Linear Programming (Chapter 12)

In linear programming question, correct graph is of 2 marks

1 Question of 6 marks will come of Chapter 8 Areas

In Area question, correct figure has 1 marks

1 Question of 6 or 4 marks will come of Limit as a sum or Definite Integral

1 Question of 6 or 4 marks will come for finding Inverse of Matrix (by Properties of Matrix or Determinant)

1 mark question has no step marking. If answer is wrong, 1 mark is cut.
 Chapter 13 Probability Random Variable question will come  4 marks or 6 marks