-
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 :
-
- 45%
- 50%
- 51.4% approx.
- 54.6% approx.
- 45%
Correct Option: C
Given , The arithmetic mean of the scores of a group of students in a test = 52.
Let mean score of remaining 55% = y
According to question ,
| 52 = | 20 × 80 + 25 × 31 + 55 × y |
| 100 |
⇒ 5200 = 1600 + 775 + 55y
⇒ 55y = 5200 –1600 – 775
⇒ 55y = 2825
∴ y = 2825 ÷ 55 = 51.36 ≈ 51.4%
