Problem-Solving and Data AnalysisMediumMissing value from a known mean
Problem-Solving and Data Analysis practice question
The mean of five test scores is 80. Four of the scores are 72, 85, 78, and 90. What is the fifth score?
Answer: 75
The five scores total 5 × 80 = 400. The four given total 325, so the fifth is 400 − 325 = 75.
Common wrong answers
- If you answered 80
- 80 assumes the fifth score equals the mean, but the other four average 81.25.
- If you answered 325
- 325 is the total of the four given scores.
- If you answered 81.25
- 81.25 is the mean of the four given scores.
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