The question paper has only $3$ questions. There are $3$ ways a student can attempt a question.
- Attempt correctly
- Attempt wrongly
- Not attempted
Each row lists number of students who attempted the question correctly , wrongly and who did not attempt.
Sum of these, of any row gives the total strength of class , $21+17+6 = 44.$
Average marks obtained by the class in the examination,
$= \dfrac{\text{(Total marks(Q1)}+\text{Total marks(Q2)}+\text{Total marks(Q3)})}{\text{Total strength of class}}$
$=\dfrac{((2\times 21)+(3\times 15)+(2\times 23))}{44}$
$=\dfrac{133}{44}= 3.02$
Note : There is no negative or partial marking for the wrongly attempted and the non-attempted questions.