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 choice from the following answers:
A) 45	B) 50	C) 51.4 approx.	D) 54.6 approx.	E) 54
Let the required means score be x. Then,   20 * 80 + 25 * 31 + 55 * x = 52 * 100   = 1600 + 775 + 55x = 5200   = 55x = 2825   = x = 565/11 = 51.4.   ANSWER:51.4 approx.
<result>C</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: