In a class, there are three groups A, B and C. If one student from group A and two students from group B are shifted to group C, then what happens to the average weight of the students of the class?
Answer & explanation
Answer: (c) It remains the same.
Shifting students between groups inside the class changes the group averages but not the class as a whole: the same students with the same total weight remain. So the class average stays the same.
- Class average = total weight of all students ÷ number of students in the class.
- Moving students from A and B to C keeps every student in the class.
- Both the total weight and the head count are unchanged, so the class average is unchanged.
Remember · Ask which total is being averaged; moving members within that total leaves its average unchanged.
Question and answer: UPSC's official GS Paper II (2020, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·