GATE CS 2014 Set 3 QGA-5 — General Aptitude

To find the average of the marks obtained by the class, we first need to determine the total number of students in the class and the total marks scored by them.

Step 1: Find the total number of students

For any question, every student in the class must fall into one of the three categories: Answered Correctly, Answered Wrongly, or Not Attempted. Thus, the total number of students ($N$) is:

$$N = \text{Answered Correctly} + \text{Answered Wrongly} + \text{Not Attempted}$$

Using the data from Question 1:

$$N = 21 + 17 + 6 = 44 \text{ students}$$

(We can verify this with Question 2: $15 + 27 + 2 = 44$, and Question 3: $23 + 18 + 3 = 44$. The total strength of the class is indeed $44$. )

Step 2: Calculate the total marks obtained by the class

Since there is no negative or partial marking, marks are only awarded for correct answers:

• Marks from Q1: $21 \text{ correct} \times 2 \text{ marks} = 42$
• Marks from Q2: $15 \text{ correct} \times 3 \text{ marks} = 45$
• Marks from Q3: $23 \text{ correct} \times 2 \text{ marks} = 46$

$$\text{Total Marks} = 42 + 45 + 46 = 133$$

Step 3: Calculate the average marks

$$\text{Average Marks} = \frac{\text{Total Marks}}{\text{Total Students}} = \frac{133}{44} \approx 3.0227$$

Thus, the average marks obtained by the class is approximately $3.02$.