The arithmetic mean of the scores of a group of students in a test was 72. 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 most appropriate option.
A) A)81.40
B) B)81.70
C) C)87.72
D) D)81.10
E) E)81.29
Let the required means score be x. Then,   20 * 80 + 25 * 31 + 55 * x = 72 * 100   = 1600 + 775 + 55x = 7200   = 55x = 4825   = x = 565/11 =87.72   Answer:87.72
<result>C</result>
The arithmetic mean of the scores of a group of students in a test was 72. 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?