In a school, the mean score of the 30 students of Section A in a test is 62 and the mean score of the 20 students of Section B in the same test is 72. What is the mean score of all 50 students taken together?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 66
The combined mean is the total of both groups divided by the total number of students; it is not the simple average of the two means, because the groups are of different sizes.
Total score of Section A \(=30\times62=1860\)
Total score of Section B \(=20\times72=1440\)
Total score of all students \(=1860+1440=3300\)
Combined mean \(\displaystyle=\frac{3300}{50}=66\)