The average weight of 25 students of section A of a class is 60 kg, whereas…
2022
The average weight of 25 students of section A of a class is 60 kg, whereas the average weight of 35 students of section B of the same class is 62.5 kg. Find out the average weight of all the 60 students of the class.
Answer: D. 61.46 — CONCEPTFor groups of different sizes, the combined average is a weighted average, not the simple average of the group averages. Each group contributes its…
- A.
60.5
- B.
62.2
- C.
61.2
- D.
61.46
Attempted by 3 students.
Show answer & explanation
Correct answer: D
CONCEPT
For groups of different sizes, the combined average is a weighted average, not the simple average of the group averages. Each group contributes its total value, calculated as group size multiplied by group average.
APPLICATION
Section A contributes 25 × 60 = 1500 kg of total weight.
Section B contributes 35 × 62.5 = 2187.5 kg of total weight.
The combined total weight is 1500 + 2187.5 = 3687.5 kg.
The combined average is 3687.5 ÷ 60 = 61.4583… kg, which rounds to 61.46 kg.
CROSS-CHECK
The combined average must lie between 60 kg and 62.5 kg and be closer to 62.5 kg because section B has more students. The value 61.46 kg satisfies both checks.
RESULT
The average weight of all 60 students is 61.46 kg.