The average marks of 40 students in an examination is 34. Later it is found that the marks of one student were wrongly entered as 62 instead of 26. What is the correct average marks for the class?

Introduction / Context:
This question involves correcting an average when one value has been mis-recorded. It is a very common type of aptitude problem related to data accuracy and averages.

Given Data / Assumptions:
- There are 40 students in the class.
- The initially computed average is 34 marks.
- One student's marks were incorrectly recorded as 62 instead of the correct value 26.
- We must find the corrected average.

Concept / Approach:
First, we find the incorrect total marks that led to the wrong average by multiplying the average by the number of students. Then we adjust this total by subtracting the wrong value and adding the correct value. Finally, we divide the corrected total by 40 to obtain the correct average.

Step-by-Step Solution:
Step 1: Incorrect total marks = 34 * 40. Step 2: Compute 34 * 40 = 1360. Step 3: One student's mark was entered as 62 instead of 26. So we must subtract 62 and add 26 to correct the total. Step 4: Correct total marks = 1360 - 62 + 26. Step 5: Compute 1360 - 62 = 1298, then 1298 + 26 = 1324. Step 6: Correct average = 1324 / 40. Step 7: 1324 / 40 = 33.1.

Verification / Alternative check:
You can check that the correction made is a net reduction of 36 marks (because 62 minus 26 is 36). So the correct total should be 1360 - 36 = 1324, which agrees with the detailed calculation. Dividing by 40 gives 33.1, confirming the answer.

Why Other Options Are Wrong:
- Option 33.3: This corresponds to a total of 33.3 * 40 = 1332, which is 8 marks higher than the corrected total.

- Option 33.5: This would imply a total of 1340, which does not match the proper correction.

- Option 33.7: This corresponds to an even higher total, again inconsistent with the given error.

Common Pitfalls:
A common mistake is to directly average 34 and the difference between 62 and 26 or to treat the correction as affecting the number of students. Another frequent error is to forget that the difference between wrong and correct value must be applied to the total, not to the average directly. Always adjust the total first, then recompute the average.

Final Answer:
The corrected average marks of the class is 33.1.