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Railways PYQCBT 1 2016

RRB NTPC · Question 85

The arithmetic mean of the marks scored by students of a class is 58. 20% of them secured a mean score of 60. The mean score of another 30% of the students was 40. The mean score of the remaining students is

  1. 65

  2. 66

  3. 68

  4. 70

Show answer & explanation

Answer: (C) 68

Explanation

Overall mean 58 = 0.2 × 60 + 0.3 × 40 + 0.5 × m, where m is the mean of the remaining 50%. So 58 = 12 + 12 + 0.5m, giving 0.5m = 34 and m = 68.