1.

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:1). 50%2). 51.4% approx.3). 54.6% approx4). 45%

Answer»

LET there be 100 students in the group.

The total score of the group = 5200

The total score of the brightest 20% students = 80 × 20 = 1600

The total score of the dullest 25% students = 31 × 25 = 775

The total score of the other students = 5200 – (1600 + 775) = 2825

The mean score of remaining 55% is = 2825/55 = 51.36 = 51.4 APPROX.


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