Problem-Solving and Data AnalysisHardCombined mean of two classes
Problem-Solving and Data Analysis practice question
Class A has 20 students with a mean test score of 70. Class B has 30 students with a mean test score of 80. What is the mean score of all 50 students?
Answer: 76
(20 × 70 + 30 × 80)/50 = (1,400 + 2,400)/50 = 76.
Common wrong answers
- If you answered 74
- 74 weights the classes the wrong way round.
- If you answered 75
- 75 averages 70 and 80, ignoring the class sizes.
- If you answered 3800
- 3800 is the total of all scores, not the mean.
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