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CA Foundation · Quantitative Aptitude · Measures of Central Tendency and Dispersion

In a class, the 30 boys have a mean score of 60 and the 20 girls have a mean score of 70 in a statistics test. What is the combined mean score of all 50 students?

The combined mean is 64. Total marks of boys are 30 × 60 = 1,800 and of girls 20 × 70 = 1,400, giving 3,200 for 50 students. Dividing gives 64. The simple average of 65 is wrong because boys outnumber girls.

  1. A65
  2. B64Correct
  3. C66
  4. D62

Explanation

Combined mean = (30 × 60 + 20 × 70)/50 = (1,800 + 1,400)/50 = 3,200/50 = 64. The option 65 is the simple average of 60 and 70, which ignores the unequal group sizes.

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