Average weight correction in a class of 60 students: The average weight of 60 students was computed as 40 kg. Later, it was discovered that one student's weight had been entered as 36 kg instead of his actual 33 kg (i.e., recorded 3 kg too high). What is the correct actual average weight of the class after fixing this single error?

Introduction / Context:
The question tests weighted averages and error correction when one item in the dataset was misrecorded. We adjust the total sum by the discovered error and then recompute the average.

Given Data / Assumptions:

• Number of students = 60
• Originally computed average = 40 kg
• One entry recorded 36 kg but actual is 33 kg (3 kg over-reported)

Concept / Approach:
An average is total sum / count. If one item was over-reported by 3, the true total is original total minus 3. Recalculate the average using the corrected total and the same count (60).

Step-by-Step Solution:
Original total = 60 * 40 = 2400 kgError amount = 36 - 33 = 3 kgCorrected total = 2400 - 3 = 2397 kgCorrected average = 2397 / 60 = 39.95 kg

Verification / Alternative check:
Replacing 36 with 33 lowers the average by 3/60 = 0.05. So 40 - 0.05 = 39.95 kg, confirming the result.

Why Other Options Are Wrong:
39.90 kg and 39.80 kg subtract more than the 3 kg error allows; 40.00 kg ignores the correction; 39.65 kg overcorrects the total.

Common Pitfalls:
Forgetting that the error affects only one entry, or dividing the error by the wrong count. Always adjust total first, then divide by n.

Final Answer:
39.95 kg