The arithmetic mean of the scores of a group of students in a test was 52. The brightest 20% of them secured a mean score of 80 and the dullest 25% a mean score of 31. The mean score of remaining 55% is: (approx.)?
Question
The arithmetic mean of the scores of a group of students in a test was 52. The brightest 20% of them secured a mean score of 80 and the dullest 25% a mean score of 31. The mean score of remaining 55% is: (approx.)?
Solution
To solve this problem, we can use the concept of weighted averages.
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First, we know that the average score of all students is 52.
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We also know that the top 20% of students have an average score of 80 and the bottom 25% of students have an average score of 31.
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We need to find the average score of the remaining 55% of students.
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We can set up the following equation using the concept of weighted averages:
(20% * 80) + (25% * 31) + (55% * x) = 100% * 52
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Solving for x gives us:
x = (52 - (0.20 * 80) - (0.25 * 31)) / 0.55
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Calculating the above expression gives us:
x = (52 - 16 - 7.75) / 0.55 = 28.25 / 0.55 = 51.36 (approximately)
So, the mean score of the remaining 55% of students is approximately 51.36.
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