Explanation
Step 1: Find the initial total sum of marks
Number of students =30
Initial average =45
Step 2: Calculate the total increase in marks
The marks were increased by 24 and 34 in two cases.
Step 3: Find the corrected total sum
Corrected Sum=Initial Sum+Total Increase
Corrected Sum=1350+58=1408
Step 4: Calculate the corrected average
Corrected Average=Total StudentsCorrected Sum
Corrected Average=301408≈46.93
Shortcut Method:
Instead of calculating the large sum, you can find the increase in the average directly:
Increase in Average=Number of StudentsTotal Increase
Increase in Average=3058≈1.93
Corrected Average=45+1.93=46.93
Conclusion:
The value 46.93 is closest to 47.
Correct Option:
(d) 47
