The arithmetic mean of the scores of a group of students in a test was 42. 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 choice from the following choices
A) A)61.4.
B) B)51.7
C) C)33.18
D) D)51.1
E) E)51.2
Let the required mean score be x. Then,   20 * 80 + 25 * 31 + 55 * x = 42 * 100   = 1600 + 775 + 55x = 4200   = 55x = 1825   = x = 33.18   Answer:33.18
<result>C</result>
The arithmetic mean of the scores of a group of students in a test was 42. 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?