| 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 source of 31. The mean score of remaining 55% is |
A) 45%
B) 50%
C) 51.4% (approx)
D) 54.6% (approx)
Correct Answer: C
Solution :
| Let mean score of remaining 55% = x |
| \[52\,\,=\,\,\frac{20\times 80+25\times 31+55\times x}{100}\] |
| \[\Rightarrow \] \[5200=1600+775+55x\] |
| \[\Rightarrow \] \[55x=5200-1600-775=2825\] |
| \[\therefore \] \[x=\frac{2825}{25}=51.36\,\text{(approx)}\] |
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