CMA Foundation · Fundamentals of Business Mathematics and Statistics · Measures of Central Tendency and Dispersion
The mean marks of 30 students in section A is 60 and of 20 students in section B is 70. What is the combined mean marks of all 50 students?
The combined mean is 64 marks. The total marks are 1,800 plus 1,400, which is 3,200, and dividing by 50 students gives 64. Simply averaging 60 and 70 to get 65 is wrong because the groups differ in size.
- A65
- B64Correct
- C66
- D62
Explanation
Total = 30×60 + 20×70 = 1800 + 1400 = 3200. Combined mean = 3200/50 = 64. Option 65 is the simple average of the two means, which ignores unequal group sizes.
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