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?  Choose the correct answer.
A) 51.4  B) 55  C) 56.4  D) 52.2  E) 60.8
Let the required mean score be x   20*80 + 25*31 + 55*x = 52*100   1600+775+55x = 5200   x = 51.4   51.4nswer is 51.4
<result>A</result>
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?