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In a seminar, 18 participants scored an average of 72 on an assessment and the other 12 participants scored an average of 82. What was the average score of all 30 participants?
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Correct answer
B
Weight each group average by its number of participants: (18 × 72 + 12 × 82) ÷ 30 = (1,296 + 984) ÷ 30 = 2,280 ÷ 30 = 76.
The larger group, 18 participants, scored the lower average of 72, so the combined average must sit closer to 72 than to 82, below the simple midpoint of 77.
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